Well you already have a signature to get some extra bitcoins, that's a good first step I think.
And also a income wich you already spending on bitcoins, I dont know how much you earn but part time isnt alot probably.
Maybe you could start a homework business at your school, where you do people's homework and let them pay money or bitcoins to you.

Or maybe invest in some altcoin and do some daytrading with them, or sell them when there is a pump to get some extra bitcoins.