Get a scouter that shows dragon ball locations then go to an area with your lvl mobs or higher keep looking for the mob with the dragon ball icon just keep searching and killing and if lucky you get a drop.

Just keep doing it the more times you do the biger chance is that you will get a drop.

and also what is a lvl mob and if u can add me and maybe i can get some help my ign is uchihaItachi

Mob is monster. Go to a mob (monster) with your level or higher.