What kind of music are you into and what do you play?

IMSLP has a ton of stuff.

I guess this is rather niche, but I go to thesession a lot for fiddle tunes. They are ostensibly an Irish traditional music site, but their collection is a vast community-led effort and there’s all sorts of stuff of varying genres on there. Folk music in general is improvisational by nature, and what’s interesting about thesession is you will find multiple versions (aka settings) of a given tune as it’s played by different artists or in particular regions. None of them are “right” per se, but it gives you some ideas when trying to work out your own style.