May 8th should not be a very busy day so I'd wait and purchase passes only if I saw I needed them once I was there. You'll zip through lots of rides in the morning before any significant lines start to form.
The order of parks depends on what kind of attractions you like the most. If you're a coaster person, I'd start with IOA but if you don't like the wilder rides, I'd start with the Studios.
Assuming you like coasters, I'd start with the IOA park. Get there about 45 minutes before the scheduled opening to be among the first to enter, you'll have that much more time to cover ground. Once inside, go to the left and ride The Hulk and Spiderman a couple of times each if you like since lines will be super short (5 minutes or so) in the morning. Then make your way around the park doing anything else that interests you. Watch your time and do what you can til late morning.
Then just before lunch, I'd head to the Studios and hit the highlights there. Do the most popular attractions (Mummy, MIB, the Simpsons) first. Don't waste time on your secondary list til your have-tos have been done.
I'm sure you'll get lots great tips but that's what I'd do, and have done.
Good Luck!