Collect all the evidence you have, emails, receipts, the whole nine yards. A lot of times court will find online stuff sketchy, because the defendant can claim "it was my friend using my account, lol". Any real life evidence you might have is a good thing to have on hand. Also make an organized time line with printouts you can give to the judge. $600 is a couple months rent for me, so I can sympathize with your desire to have that money refunded.