The difficult thing about using Skitty is that Normalize removes all type coverage. So, coming up with a decent movies for Skitty is a real chore. However, looking at what TMs she can learn I have come up with this set:
- Fake Out
- Wake-Up Slap
- Blizzard/Shadow Ball/Double Team/Charm
There are probably better sets, but this I the best I could come up with. Fake Out is nice because it has awesome range, STAB and flinch hax. Sing is a useful utility move to put opponents to sleep, allowing you to heal or run away. It also sets up for big damage with STAB Wake-Up Slap (with Normalize). The final move is a toss-up between Blizzard, a powerful move that hits every enemy in the room, Shadow Ball for a line-of-sight attack (Water Pulse works too and has the option to confuse), Double Team for evasion hax, or Charm to make physical attackers a non-threat.
I played Explorers of Darkness with Meowth, who has a very similar move pool to Skitty, so I feel your pain when fighting Dialga.