For the first ride, I recommend choosing one of these three rides: YOLOcoaster, Tatsu, or X2. Once you are done riding one of these, go to the back of the park and ride the other two later. If you have a Discover card, use the 5 minute early entry line. If you are not able to make it to the park's opening, I'd just go on Orient Express, ride Superman, than go to the back of the park immediately. Apocalypse, Batman, Green Lantern, Riddler, Lex Luthor, Colossus, and Scream don't have much of a line if any in the first 90 minutes. X2 has less of a line around 3:00. Food: Don't go to Food Etc. unless you want to experience the "amazingness" of it.
I have no idea about crowds since I never visited SFMM during a May weekday, though I doubt it will be busy.
Thanks XYZ! Maybe I'll just start with X2 since it seems nearest to the entrance. What's your take on YOLOcoaster? It looks really fun despite seeming kind of short (the videos make it seem short anyway) I really can't wait to do it all; my only credits for 2014 are the coasters at the WDW resort.