Hey Cocoboy - sorry for the delay in responding,
You'd be ok adding one yellow tang to a 75 gallon tank but I'd not have more than one. They can be territorial and will slap at each other with the spines they can stick at the base of their tails. Only having one tang is my recommendation and you can keep other fish in the tank with them since they are mostly aggressive with their own kind. They should get along fine with clownfish.
There isn't a whole lot to choose from when it comes to schooling
saltwater fish that are commonly available. However, do a google search on Chromis cyaneus (blue chromis) and Chromis viridis (
green chromis) which I think are schooling saltwater fish that should get along ok.
Look here too -
http://www.fishlore.com/profiles-blue-chromis.htm http://www.fishlore.com/profiles_blue_green_chromis.htm
If you want gobies - check out the Elacatinus oceanops (neon blue goby). It's a cleaner fish but it should also accept frozen, live and flake foods.
http://www.fishlore.com/profile-neongoby.htm
You're at the really fun part in my opinion - researching the fish and inverts. Spend more time at the beginning and you'll have less headaches and more enjoyment going forward.
Mike