How to unlock Objects:
1. Complete all story missions.
2. You get 5 from Shenron
3. You need to fight 5 times on easy,normal and hard in the world tournament with 8 and 16 Peoples. (Makes a total of 30 Tournaments)
There are 3 good methods to get Dp's:
1. Play at the Punching machine.
2. Play extreme Battle against Vegeta. he brings a lot of Dps and is really easy.
3. Play against Vegeta in the extreme battle and then make one Dragon Ball fight. After you got 7 Dragon Balls you can get 30.000 DP from Shenron.
I also reccomend to use the Champions Belt which you will get from Shenron. You get 25 % more DP's after battles.