It depends on what fish you go with , I keep 12 in my 90 but somehow I managed to over do it with blues , soon as I find some colorful I will swap out a few blues to make room,
don't forget to give allowance for fish to grow , when small it may not look over crowded and you think to yourself I can add a few more , but once they start growing you see you over did it and scratch head as you fell for all of them on which ones to get rid of .
as for corals it all depends on your lighting , I always suggest start with zoa's/palys
and other softies like leathers , once you get used to taking care of those you can start moving up the ladder to LPS
torch , hammers , elegance ect , now after that if you have really good lights you could try your hand at SPS
What ever you choose to do fish coral ect always go slow you don't want to over load the tank to fast as it is new .
this was my 90 build the only difference was I transferred 2 established tanks to the 90 so basically I didn't need to reestablish BB as I used all my existing rocks , filters ect , look forward to see your tank once you get it under way
SEAWEEDS 90g BUILD/TRANSFORMATION