A good way to find stuff is to follow hashtags you are interested in. You start seeing people who post stuff you like and follow them as well. Want art? Follow #mastoart. Want stuff about programming? Follow #programming. Then you start seeing artists and programmers and you can follow them to see their other posts. They boost something and oh that is interesting too so you follow that person too. You kinda gotta get the ball rolling by just following stuff.

There is not really an algorithm on masto which is simultaneously its greatest weakness and strength, just people boosting stuff, just people tagging stuff. It takes a little more work to find stuff but the benefit is no one can game the algorithm. Things spread organically.