First off, what kind of mag is it?
If it takes the standard mag twist lock threads, i'd say don't worry about a good barrel now, save up for the ULE body, which uses cocker threads. AGD twist lock is going out the window, so there is no sense in really investing in it, when Cocker threads are becoming more and more the standard.
Ok, you have your barrel threads, i'd say next check out your paintball level. If you're the type of player that plays a lot and can really see dumping money into a barrel, then go for a kit! If money is tight, and you need something to get you by, but not break your wallet. I would then highly suggest getting a J&J or All American. Depending on where you go, i prefer ebay, you can find some sweet deals on barrels. Those two seem to work them best in my past experiences.
Good luck!
- Brian