I've never played New Vegas before and I was wondering if there are any mods or fixes I should be aware of before starting my first game, or if the GoG version already comes with all essential fixes.

GOG version comes with essential stability fixes, but it's good to have at least some mods :
https://github.com/xNVSE/NVSE/releases you need this for a lot of mods
https://www.nexusmods.com/newvegas/mods/51664 bug fixes
https://www.nexusmods.com/newvegas/mods/62552 performance
https://www.nexusmods.com/newvegas/mods/42507 it lets you configurate (some) mods
https://www.nexusmods.com/newvegas/mods/66537 stability/performance
https://www.nexusmods.com/newvegas/mods/53635 stability/performance
https://www.nexusmods.com/newvegas/mods/34943 gameplay

And to install mods you will need a mod manager, if you're new I suggest either https://www.nexusmods.com/about/vortex/ either https://www.nexusmods.com/newvegas/mods/54991

You can look there for other mods : https://www.nexusmods.com/newvegas/mods/?BH=0

Too many bugfixes may lead to new bugs and incompatibilities..


What I consider essential:

- 4GB Patcher (so you don't need the NVSE Launcher)
- NVSE
- Tick Fix (requires NVSE)
- Dead Money Stealth Fix

Optional:

- jsawyer (Original, not Ultimate)
- Uncut Wasteland (Main file, scenery and objects only)

Small changes that I like:

- Strip Wall Billboards
- Shishkebab Torchlight
- Powder Gang Orange Jumpsuits