Oh don't worry, I know where you're coming from. Can't say I'm really technically a teen anymore, but I'm only a couple years out and I have/still do pay for the majority of my fish and their supplies with my own money. Its really not at all a cheap hobby sadly....
A 10 gallon isn't quite as large as you might thing....do you have a good solid desk or dresser? Take a look at the dimensions of one(you can look it up online), then take a measuring tape to ANYTHING in your room you may think solid enough. You might be surprised where you could fit one....I don't even KNOW I I've managed to squeeze 12 tanks in my room. xD
As far as budget goes...have you checked around local thrift stores or Craigslist? You can often find some nice used tanks for much cheaper.
If you really can't manage a 10 gallon....then it'd be best to take the neons back or rehome them along with your Glofish. Actually if you went ahead and did that, you could keep your boy alone in his 2.5 for a while and take the time to save up for something larger with all the fixings and whatnot so you wouldn't have to rush out and spend all your money right now. Then you could start looking into proper tank mates for whatever size you choose. That might be the cheapest and easiest solution for the moment, if you'd be willing to do that instead.