Instead of asking "what should I get?", ask for what fits a set guideline that you've made up, including size, husbandry requirements, typical attitude, common illnesses/problems, pricing, and morphs. Then when you go, look for that. If you see something pretty or otherwise interesting that you don't know much about, ask the vendor what they know about it and then check a few online sources (ask around if anyone will let you borrow their iPhone if you don't have a mobile device; people are pretty nice at these things) before just buying it.
And when you go, make sure you check for mites, other parasites, scars, injuries, etc. Also ask if it's a wild caught animal or not. I got a rat snake from LLL Reptiles that was wild caught, quite a few small scars along his body plus one on his nose that's still healing up, AND he had mite eggs. There is NO WAY you can check for mite eggs, but you can check for mites. As a word of caution, soak your new additions in warm water and also spray them with an anti-mite liquid THE DAY YOU GET THEM.
Also, don't let the vendors sucker you in to buying something you don't truly need/want. Though the vendors I talked to were pretty friendly though some were a bit too busy to actually talk to me when I walked up to their table, one of them was a bit too happy to try talking me into buying some of their animals.
