Brain Buster - everyone seems to have advise on how to manage your roster, so I will not chime in there.
Instead, I will offer to you a valuable suggestion that will potential reap much benefit to you: when you have money, consider investing it into your arena, instead of acquiring young players. Your arena is your lifeblood, and you have only added 5 seats to date. For now, build some lower tier, courtside and maybe a couple of luxury boxes. Also lower your bleachers price so that you can fill all those seats, and then start adding lots of bleachers.
Once you have this set up right, then start acquiring players - once the revenue piles in, your will find managing your finances much easier.