Mode: Battle Enemies
Enemies: Geonosians
Geonosians will start coming from all directions after you walk around a little bit
Mode: Collect Studs
Go to the left, and towards the screen. In a large container on the left side of a long island contains a power-up. Walk around that island, destroy everything, and then go back to the beginning of it, where everything should start to re-spawn. Repeat this a couple times.
Mode:Stud Hunt
Hunt: 616,000 studs
There are lots of purple studs on the falling tower, in the back right corner. On the island to the right of that is a power-up. Grab that power-up before getting the purple studs on the tower and in the area.