go to route 116 and keep running in the tall grass, it will eventually appear.
In Emerald you can find Skitty on Route 116, but they are rare.
You need a moon stone to evolve a skitty.
route 116
Skitty learns assist at level 22.
Skitty can be found on route 116 However, it is very hard to find but trust me its there!
Trade it with a Pikachu.
Migrate from Ruby, Sapphire, or Emerald.
In Ruby, Sapphire and Emerald on Route 116 and are rare.
On Route 116. Rarity: Rare.
skitty does not evole by its self you need a moon stone to help skitty evolve into a skitit
according to the official player's guide for Pokemon emerald version wild lunatone is the only Pokemon that hold moon stones and they can't be caught in emerald. You need to trade a lunatone over from sapphire.
In Emerald, the only Pokemon that evolve with a Moon Stone are Jigglypuff, and Skitty. Skitty and Jigglypuff both are normal-type Pokemon. Skitty can be found in Route 116, east of Rustoboro City, and they are very hard to find. Jigglypuff can be found in Route 155, north of Rustoboro City. Jigglypuff evolves into Wigglytuff, anf Skitty evolves into Delcatty.