Right, so because Win 10 gave me a scare where I thought it might've sneakily downloaded because my Win update was lasting too long after restart (I manually update and approve all installs, however after it said it was "cleaning" things I wasn't sure if maybe something went wrong), I decided to go and backup my most important stuff.

What would you recommend? I think outlook/hotmail gives you some free space, right?

External HDD : )
I don't trust any cloud service..

I feel the best bet is to go with Google Drive which gives u 15GB free from the start, if that is not enough u can also use Dropbox which provides an additional 2GB for free. Just google either & u shd be able sign up for an account with them easily.

Personally i also prefer backups on external hdds like mike_cesara but since ur qn was which is the best free place to backup stuff online i think my ans wld be more relevant. ;)

So there are no other reliable free services besides Google Drive, Dropbox and Mega?

There's Box and Mediafire. Box has annoying file size limitations but for some reason I have 50GB free which is nice. Mediafire has likely lower but that site is awesome at utilizing my internet speed (maximizing both download and upload).

If you hold security and privacy in high regard, then the best solution is obviously to sync locally, but there are several cloud services that offer the best currently available in this regard, at least as trusting third party with your data goes.

Sync offers a free 5 GB plan with plethora of security-oriented options with encryption, while also offering apps for Windows, OS X, iPhone/iPad and Android. Of course, there's always an option of accessing from the browser.

Another alternative is OziBox with 10 GB of free storage for desktop and mobile devices, but what's specific is the fact that it has been developed by a global community.

copy(dot)com is one .. I think 15G free.

From a security perspective, Tresorit may be best. Or you can use another service and encrypt sensitive files.

I don't think HDD is a good solution for long-term storage for backups.
It is mechanical, has grease, which changes it's properties (like viscosity) over time, especially if it is not in use for several years. It is vulnerable to shocks. Don't forget about it's electronic part.
IMO, Best media for backup storage is BD-R discs, or DVD if BD-R is too expensive. It's not as convenient as HDD, but for backups it is ok. As a bonus, recorded information cannot be changed (by virus, or other undesired activity), i.e. becomes immutable.
Optical discs have drawbacks too: scratches, UV radiation from Sun. But they're relatively insignificant.

For me the best place is here :

https://giga.gg/en/

Free
500gb
encrypted

WD disks are good enough for regular backups. Fast, easy, safe.

Depends on what your "important" stuff is.

Photos of your dog? GOG installers? Dropbox away.

Your passport number and bank account info? CD, USB stick, external HD.

Just to add, THIS ^! Whats the point of getting DRM free games, and then putting them in a place where your reliant on a company?

Well, to a certain extent, however what I do is have 4 in addition to the 1 in the machine. These four cycle every 3 months, two external, two in the house. Unfortunately doing that with dvds is not possible, especially at 3gb.

Yep, and if your that worried about them breaking, have more than one, and keep an X years refresh policy, i.e. every 10 years buy a new set.