Firstly I know that it would make more sense of Babidi to be on the Earth, however Earth has more than enough areas at the moment. In order to succeed you must clear a set number of floors, each containing one fight. The rewards are;

1 Floor: 5,000 PL, Fight Stats
2 Floors: 10,000 PL, Fight Stats
3 Floors: 30,000 PL, Fight Stats
4 Floors: 200,000 PL, Fight Stats

Later on I might put up recomended power levels, though that kind of takes the fun out of it. I'd suggest not going past the first floor for now.