A strong attack should take out Sneasel pretty quickly.

Golbat can be defeated with a Psychic or Electric attack.

Magneton - Ground, Rock attack.

Gengar - Psychic attack.

Alakazam - Try using some Electric attacks, any Dark moves you just so happen to have would be the best.

3rd Evo Starter - Depends on what type it is. Grass - use Fire, Water - use Electric/Grass, Fire - use Water.

On Monday nights, Mt. Moon will feature some dancing Clefairy. If you go up to them they will scatter. Go up to the rock they were at and you will find a Moon Stone.

There's really nothing more to Mt. Moon. It's very short now, compared to what it was like in Red, Blue, and Yellow.

Inside you can find the rare Clefairy. Find a male and female and you can breed them at the Breeding Center for a Pre-Evolution Pokemon.

Jigglypuff are outside Mt. Moon on either side. Find a male and female and you can breed them too for a Pre-Evolution Pokemon.

If you're done with that, head back to Pewter then go all the way South. You don't need to stop by Viridian City, or Pallet Town, just go to Cinnabar Island, or what used to be Cinnabar Island....