Dat crappy movepool. Special Attack isn't even really usable, but whatever. =/
I would do:
Curse: Boosts stats and make it hard to take down.
Earthquake: STAB, and it's Earthquake, why not?
AncientPower: Gets pseudo-EdgeQuake, and has a chance to raise stats.
Return/Dynamic Punch/Sludge Bomb/Toxic: Well, there aren't many options. Return scores fantastic neutral coverage, while Dynamic Punch can still be good for coverage and power if you don't mind the shaky accuracy. Sludge Bomb can be used to hit Grass types. Toxic can just be filler to slowly eat away at the enemy's health.
Surf: STAB and good power + accuracy.
Ice Beam: Coverage and good power. Hits Grass and Dragon types Surf can't hit.
Earthquake: STAB, again, it's Earthquake, 100 BP 100 Accuracy. What's not to like?
Return/Dynamic Punch/Toxic: These are explained above.