Easy level ups on that docter gero level
Ok first you have to fly to the docter gero level the beat dr gero the second time go up there would be a save spot.
Save if you want then go left and there would be 3 purple tiger enemies.
Defeat them, then you wil see a gate that only goku can go through, walk right up to it then the dinosaur bihind the gate will notice you,then it will run up to you, some people might think that you can't attack through a locked door but those people are wrong!
So try to attack it while it's against the wall and it will do damage.
Keep attacking until it's dead and it will give you heeps of exp!
Then go out of that area then go back in it and keep on repeeting the progress!