What to buy on humble store

Anything DRM-free: https://www.humblebundle.com/store/search?drm=download

The current DRM-Free sale is very limited, I might wait until early/mid January as they historically have had a Winter sale at that time (after Steam sale has finished). Ruiner might even go back on sale at that time.

However, the timing of this small "holiday DRM-Free sale" is kind of weird, so I'm not really sure what HB is planning and it could be different than years past due to the IGN takeover.

Same boat. I waffled on getting Cuphead, Hellblade and Ruiner, and let all three slip through my fingers. I'll probably work on my backlog rather than pick something up from the current sale. I think I'll see what comes up in the spotlight sales, the next monthly and any New Year's specials they have.

Speaking of backlogs, however: Satellite Reign, Frozen Synapse and We Are the Dwarves are ones in my backlog that are now ~90% off through Humble. They're not going to offer the same gameplay experience as Ruiner, but the first two have a cyberpunk aesthetic (as do the Shadowrun games, also on sale) while We Are Dwarves will offer melee combat and a sort of bullet time. I haven't played any of them yet, but they're on my short list and at about the best non-bundle prices I've seen.

im looking for something else to buy for 11€ on humble store, any suggestions?

I'd suggest hanging onto your loot until the next time the game you want (Ruiner) goes on sale.

I haven't bought a lot of games there except for bundles because IMHO there are way cheaper options on Steam or GoG. Most of the games there seem pricey to me compared to other digital stores. For the price range you suggested I guess you could buy this month's bundle.

wow, i never noticed the HB store was so expensive O_o
i can't recommend anything worth paying their insane prices even on sale...