Orion is a people eater. even a long line on that moves fast.
do Diamondback, MT, and Beast first. (that's the order you'll get to them if you go right).
if you go straight back behind the Tower, you'll hit Beast, MT, then DB in that order.
there is a Skyline Chili near the front gate, that was good. the "Tom & Chee" (grilled cheese place) in front of Diamondback is really good too. I'd recommend both of those.
the menu at the french restaurant near the tower looked great too, tho we didn't try it.
yes, you can ride the train without getting off and going into the waterpark.
dont' sleep on Adventure Express . a very fun mine train, or the Bat - never has much of a line, since it's such a walk to get to the station (it's near Banshee for entrance to the Bat queue)
you should move heaven and earth to figure out a way to get FL+ tho. .. even if not too busy, FL+ will cut out a TON of the walking in the queuelines.