I think the first thing you should get is a $50 PSN card and get Playstation Plus, then you can play a bunch of games for the price of one.
Edit: Also with PS+ you will get PS1 Classics which you can use on your Vita when they bring out the firmware update and get discounts on some PsP games.
The PS blog has also hinted they are working on PS+ in some way for Vita. Though they didn't give any details.