Compost is gold... erm bitcoi... eh... compost is great. Each plant needs a bit different fertilizers, but compost is almost universal. Some plants don't like too much of it (like parsley) but not many. You can plant zuccini or tomatos directly into pure compost and it works great.

Some use commercial fertilizers to add since the blooming starts. But you can add a bit more compost instead... like every two weeks? Bird, cow, horse poop is the most typical, just make sure your plant likes it. You can buy it in a concentrated form too.

I'm an amateur, so watch some videos and read article or two about growing what you grow.

It also depends on how fertile is your soil, that differs a lot.

Also it sometimes takes about one season to insects/fungi etc to adapt to what you're growing, so the first season can be great and the the next one maybe less so.