How are new players suppose to do Dokkan events? They're too hard.
It's a gradual process; if you've gotten a bunch of good undokkaned units you still have to go from the easiest events to the hardest. If you have SSJ Gogeta, that's a pretty easy fight that gives an incredibly good unit.
Story mode is pretty easy and gives a lot of Dragon Stones, so you can stick to that until you get a good team. Same for story events (like the Yo! Son Goku Returns movie event running now). And of course, get team Z-awakened before you bring it to the dokkan event.