It's official...The best way to get dragon balls is PQ 15. I was doing the quest to get "Death Slicer" to complete my collection of all attacks and to get a Z rank. I played it 4 times and 3 out of the 4 I got the time patroller and all 3 times I got a dragonball (2,3,7 star) Edit: Did it 2 more times and got both material items that time...Definitely just luck. You have to beat Frieza in 2 minutes for the TP to appear.