Greyhound goes from gates 79 & 80 and Academy from gate 1. You should be fine getting there about 20-30 minutes ahead for both buses. Academy also has a bus going from Port Authority to Caesar's at 8am (also goes to Showboat). I believe that Caesar is the first stop and then it goes on to Taj Mahal. I've taken the 8am Greyhound bus to Caesar on a Sunday morning and its not crowded.
