Link to the official GOG Mod Spotlight.
A few things to note:
-As always you have to ensure that the files that the mod files that you want to use are loaded after your game files. That includes esp and bsa files.
you may have to ensure that your games bsa files don't get loaded after a mod. Thiev has now added a workaround to the installers but using a mod manager to do this is reccommended. (Thank you very much, Thiev.)

-fixing a crash: Some people have experienced crashes after the Bethesda logo that weren't caused by installing mods in the wrong order. They could fix this by removing their save game folder that contained old saves (from a non-GOG version). Since the old Oblivion saves might end up in the cloud, cloud saving might have to be disabled as well. I don't know if it's really because of the save games or because of .ini files and can't test that. marmormurmel described how to fix this crash: -The Oblivion Script Extender (OBSE) requires you to download and install the current obse_loader!

These are mods that I recommend checking out.
I'm wondering what mods you GOGgers recommend to fix level scaling. Also, I'd like to know your opinions on this mod list! :) Do you see any problems with it and what are your must-have mods?

In order to avoid problems with mods or solve them:
Use a mod manager like Oblivion Mod Manager. This will allow you to uninstall mods safely and to get them to load in an order that makes sense.

The following mods I recommend without any doubts:
the unofficial patches.
Oblivion
Shivering Isles
DLC

Restores a chapel in one of the cities:
Anvil Chapel Restored

Fixes the stupid crash when exiting the game:
Fast Exit
(apparently the Oblivion Stutter Remover does so, too)

a graphics/lighting/weather mod:
Natural Environments (and/or something else like)

a water mod:
enhanced water
or
Skyrimized Water (or something else)

a better distant ground texture:
Landscape LOD Texture Replacement

animated containers like in later Bethesda games:
Harvest Containers

For a completely different game world:
Nehrim (total conversion)

A fix for that level scaling!!!
this is a really tough one. On the one hand it is the most important change to Oblivion that you can make but on the other hand the possible mods tend to change much about the game and aren't that well compatible.

Francesco's Creatures and Items - including the optional content. (Suggested by etb)

Maskar's Oblivion Overhaul

Oscuros Oblivion Overhaul

Oblivion Scaling Unclustered

Leveling Quickfix

You should probably install these:

This fixes the problem that touching objects is a crime:
put it in its place

I've never had the DLCs before but I hate it when Add-ons start quests before your first quest is over:
oblivion dlc delayers

The following mods are great gameplay enhancements:
Recommending these is also not easy because I don't know how compatible and stable these mods are because I've never played long playthroughs with them

Witness system for crimes and regional bounty:
Crime and Guard Overhaul with Regional AND Provincial bounty

Item ownership (NPCs shouldn't know which item is stolen):
Stolen Item Ownership - or use the console when it makes sense "SetOwnership"

Has anyone experience with these mods that give merchants limited gold?
Enhanced Economy
or
Living Economy

Also check out these:
Graphical enhancements:
Oblivion Reloaded
Enb
Qarl's Texture Pack III Redimized

more objects visible in the distance:
Really AEVWD

dynamic shadows (don't have too high hopes):
shademe enhanced - isn't perfect!! consider Oblivion reloaded as it says on the mod page

UI:
darnified UI -It's great but the installation is annoying.

first person body:
Oblivion - Enhanced Camera -really good, the only disadvantage is that animation mods might not look acceptable in first person (like natural walk)

movement physics:
Improved movement physics

more varied and unique landscape:
Unique landscapes

requirements of some mods:
universal silent voice
a mod manager
OBSE
blockhead
MenuQue
Real-Time Interactions

If you want to overhaul your game significantly take a look at these mod compilations:

This is a guide to create a functioning incredibly heavily modded Oblivion install. I have never tried it because the Oblivion Deluxe Edition was limited to Steam, but it is probably an amazing mod-setup for a later play-through.
[Oblivion] Modding Guide for Easy Install - "Maximizing Oblivion" (Modding Gallery)
https://www.youtube.com/watch?v=15wDKl9zDSA

Another overhaul that covers the leveled lists: The loot and the encounters. It was been suggested by anothername:
FCOM Convergence
http://www.nexusmods.com/oblivion/mods/12249/?
it includes the above mentioned Oscuros Oblivion Overhaul (in the OP) but contains three more mods to add many more monsters and loot.

If you want to add any more mods to a game modded with either one of the above mod compilations, you should know perfectly how to merge leveled lists and ensure game stability.

And another modding guide: https://medium.com/the-backlog-gog-com-stream-team-blog/an-oblivion-modding-guide-9274b2640231

I want to personally invite you to hand held guide to bring Oblivion screaming 10 years into the future.

Its from Predcaliber, hes known for total game overhauls and finding the best mix of graphics and usability. I have personally used this guide and have only added a few other mods to get it up to my desired game. I highly recommend using the Nexus Mod Manager for the below. (see attached image to show the color, dof, and lighting, textures) as a note you don't need EnB, its not for everyone... but the rest are fantastic!

Oblivion XP Update -- makes the need to min/max and monitor skills obsolete
A Brotherhood Renewed -- properly ends and gives a better close to the dark brotherhood questline
A Brotherhood Renewed Patch for OblivionXP
DarNified UI -- a must have, use the Nexus Mod Manager for installation
Elven Map Redux -- colored and detailed world map for Oblivion
Khajiit Night-Eye Toggle -- toggle-able night eye instead of a power to activate on timer
Denock Arrow -- requiver any arrow you nock on your bow (an absolute must)
Quest Award Leveller -- tons of items are given to you based off level... this auto levels the gear as you level.
Supreme Magicka -- tons more spells and enchantments without breaking the game or lore

Maskars Oblivion Overhaul -- one of if the the best content and game overhauls for oblivion it adds so much that feels like it should have been there from the start. I cannot recommend this enough!

Great suggestions! Especially Denock Arrow. :D

While level scaling is indeed a part of FCOM it actually only begins there: https://www.youtube.com/watch?v=MryxMaob-Jo

Its MASSIVE.

Oh, thanks for spotting that. I actually meant levelled lists in this case not level scaling... What I thought was: This mod mainly deals with everything that you meet or find "randomly" and adds a huge number of stuff, whilst changing how your level plays into the encounters. Would that be correct? :)

Hi, my game is crashing randomly ... Do you know how to fix it ? :(

Kind of. Just saying, if someone wants Oblivion as it is just with sane scaling FCOM would not be what they look for.

Its a merger of the biggest overhauls of their time done in a massive undertaking and believed to be impossible to merge; each on their own already a game changer in the literal sense. I don't know about fixing but I do know that the people that do know about fixing at least need:

- Your PC specs
- Which Oblivion version (most likely latest gog build but just to be sure).
- What mods installed
-- What order the mods are installed in
- Where the crashes happen (always at the some spot, the same action, completely random).

I honestly do not like the overhauls, I played FCOM for a while and become disillusioned. Mods should have a clear focus.
So here is my list, with "what I don't like", mods that fixes it, and maybe (comments).

"The world levels up with me ridiculously!"
Francesco's Creatures and Items, (all the optional content).
Medieval Oblivion Equipment Balance System.
(The world still levels up, but it is kinda having a master in a dnd pen and paper game. So you will still find low level monster where expected.)

"Carring around loot is so annoying!"
Luggage Companion, if you like a critter following you around. Storage sacks otherwise. Even simpler, just allow to carry unlimited weight in the Wrye Bash patch.

"I need to spend millions reloading my magic items!"
Enchantment Restore Over Time.

"I HATE minigames. I am playing a RPG or a stupid cellphone game?!?"
Persuasion Overhaul
Enhanced Economy
Lock bash omega
Real Time Lockpicking
(of course disable the Haggle minigame in Enhanced Economy)

"Why cities are in their own cell? What the heck the Bethesda was thinking?"
Open cities reborn,
Crowded Cities for Open Cities Reborn, download the "no script" version.
(Morrowind got it right, Oblivion did not... Bethesda? Are you drunk?)

"Why streets are so empty? Why the heck there are only guards and criminals
going around?"
Crowded Roads Revisited.

"I do not really -feel- the fights, they look like a clicking minigame.."
Realistic Health,
Realistic Fatigue.
(I put a much more forging settings for running, because moving around comfortably is more fun. It is during fights, that having to keep your fatigue under check makes the experience better.)

"Races are ridiculous, there are hardly any different! And besides why anyone would not play a Breton/Atronach? A part for the extra challenge I mean."
Race Balancing Project Light
(Makes the races (and birthsigns) different and interesting, there is also a non-Light version with outlandish races. As I stated in the beginning I like mods to the point so I like the Light version better.)

"I would like some extra creature..."
Creature Diversity,
Espy creatures,
FLY creatures.

Edit: Oops, sorry. I didn't realize someone else already posted the video from Zaric, though I should have figured I wasn't the only one here who would think of his mod list.

My memory might be wrong but I think I remember that the Oblivion Master file should always the the first in the load order. Maybe that helps.

I do remember also having the occasion crash back when I played; while at random situations it usually only happened after several hours of playing if it happened.

Yes, the load order seems completely horrible but I think it shouldn't even be possible for the game to start with such a load order. That's because the dependencies apparently are further to the bottom than the mods that require them. Besides, the different language might be a problem.
If your game is unstable, you have to put in the work yourself to test out where the problem lies by resetting the game to an un-modded state and adding the mods one by one.
Also: Check this post out: https://www.gog.com/forum/elder_scrolls_series/oblivion_for_linux/post9

I think, this thread should mainly be limited to mod suggestions, though, (including fixes). It's not difficult creating one's own thread here and in my opinion this is derailing it heavily. Please continue this discussion in another thread. :)

(To clarify, this thread is also supposed to be about fixes, but your problem seems to be caused by your mod load order. Problems that aren't due to the game itself are out of the scope of this thread.)

Regarding the post below: It's been so long since I last added a mod using only the launcher that I forgot that it lists the files alphabetically. According to the link to the Oblivion for Linux thread, there seems to be a problem in addition to the bsa timestamps (until a fix arrives, you have to reset the timestamps of the bsa files). However, the other problem was solved using LOOT. That means, it's probably not going to help here.

Also, thanks for your mod suggestion, Pherim. I'm sure many users are going to love that mod.

This screenshot is from the launcher, which sorts plugins alphabetically! It does not reflect the actual load order. He already posted a screenshot from LOOT in a different thread, and as far as I could tell it looked fine, but the different language may indeed be a problem. Or something completely different, it may not be related to mods at all. But he really should create a new thread for this.

Mod suggestions: Definitely Character Overhaul v2!

So what all do the patches fix?