Depends on what your goal is for said knowledge. If the purpose of learning is to have really effective cycles, I can't point to a single place and wouldn't even recommend a one-stop-shop for all your prohormone needs.
I'd just give you pointers on how to research until you do decide to try something.
Be open-minded. Make sure you understand that even the gurus don't know everything and probably even have a few things wrong in their current understanding on hormonal interactions. There a plenty of steroids that do this on paper and that in practice. So with that,
Don't discount anecdotal reports just because we don't have a working theory or explanation about the effects of any given hormone, it doesn't mean the report is not true. In fact, the only sure thing you do have IS anecdotes, because anecdotes are actual observations.
Use multiple sources and make connections and find patterns this is one I do often. Don't accept just the common or available truth/knowledge, go ahead and analyze things yourself and find the missing connections. It might require trial and error and a little faith, but in the end it will amount to you knowing vast amounts more than whats being published or talked about on the internet. You don't have to be a doctor or professional practitioner to learn ground-breaking truth.
Be keenly aware of your body's reaction/body awareness Some people are wildly ignorant of what is taking place in their body. When it comes to hormones, don't be like this. Pay attention. Take notes if necessary.
Do all this and you'll be ok.