I personally have found that ordering online is best for a rare fish you cannot find locally. If the fish you want is present locally in a LFS, you know it has made the thousands of miles trek from ocean to Georgia in one piece, and all that is left is a short car trip to your house. If you see it eat at the store, I would not hesitate to buy that fish. But definitely QT no matter where you get it from. That said, I have ordered online from time to time, again mostly for something I really wanted that could not be easily found locally (like Watanabi angel, blue spot leopard wrasse, etc.). Or sometimes Liveaquaria has crazy sales for common but expensive fish, like $89 purple tang, I snatched that up. Treat your QT not as a punishment, but as a fun first tank for you to observe and get to know the fish, while you make sure it is reasonably cleared of parasites and issues.
In QT, the big killers are ammonia and oxygen depletion, so do water changes, use bacteria in a bottle (and perhaps media from your DT), and powerhead(s) for good water flow.