Mode: Battle Enemies
Enemies: Beach trooper, Stormtrooper
Roam around the big, long C-shaped island in the middle. You will most likely spawn here. There is a power-up on the right side, on the branch of the island closest to the screen, in one of the blue boxes. You can also step on the floor buttons to raise bridges leading to other areas, allowing more troopers to come to you.
Mode: Collect Studs
Stay on the C-shaped island in the middle, and stay at the end with the power-up. Containers and plants seem to re-spawn pretty quickly, so take advantage of this. Troopers will start to make a big crowd very quickly, so keep that in mind, and manage that if you have to.
Mode: Stud Hunt
Hunt: 151,000 studs
To the right of the area on the C-shaped island with the power-up is an, open, hollow tree trunk you can hop into the contains a bunch of purple studs. These studs will give you pretty much everything you need