DP can be a bit buggy and the UI is a pain in the ass but the requirements for this crossover are very easy for you guys. I would actually recommend NOT starting early as you get free AP up until level 51, which you can just burn on the event mission. All you guys have to do for this crossover is simply play the event mission. You get credit for defeating a boss if you just tag it and others finish it off so you don't need to have any real level of power. Daily missions are just things like "enhance a card" or "earn 300xp" so that is also easy enough.