Of course the Pokedex is hard... and the Battle tower is somewhat challenging, but the contests are a bit easy, until you get to level 4 on them. But right now I'm aiming for Pokedex. I'm almost done too.
all five for a while now. working on my pearl to get 5 again. you need to beat the elite 4, win master rank in at least 1 contest category, get the platinum flag rank, register all non-event poikemon in your dex as caught, and get a 100 win streak in battle tower.