EVERY day is busy there for the most part. We've waited 1 1/2-2 hours in the past for some of the bigger coasters. We typically go on a Wednesday or Thursday to avoid the crowds, but it's still crowded. Also, they are checking bags/fanny packs/backpacks etc. at the entrance which slows things down a little. I would get there no later than 9:15. They will let you in the park before 10, but they have ropes across the "lands" so you can't line up for the rides. If you want to do Superman without a 90-minuite wait, line up at the left side of the carousel and run like crazy when the rope drops. If you don't go right away, the lines are horrendous.
Jewel always sells discount tickets. They are about 1 mile west of the park on Rt. 120 (Grand Ave) & Hunt Club Road if you don't find a discount somewhere else.