Easily gain Studs in Chapter IV, Episode 1 by building the first two control panels and pulling the lever on the left side of the room. Continue to pull the lever to collect Studs.
Outside the Cantina, destroy the two fan covers. Also, in Episode IV: Return of the Jedi, use the force on the blue chairs in the middle of the room.
To gain over 50,000 studs, go to the Podrace and use one of the speeders from the start of Episode II. These are great for hitting the pink crystals since they have better mobility. Use Subulba's Podracer when hitting the little poles. It is easier to hit them with a wide Podracer.
While playing two player, go outside the cantina and build or find a car. Have player 1 get in the car, then player 2 should press TRIANGLE near the car whie player 1 is in the car. Soon player 2 will vanish. When that happens, player 1 should get out the car. Then, player 2 can drive around in a car with no driver.
To unlock Indiana Jones, go to the bonus room in the Cantina. Enter the door labled "Trailers" and watch the trailer for Lego Indiana Jones: The Videogame. Indiana Jones can now be bought for $50,000 studs.