What's a good Grass type pokemon to have? The one I have only evolves when I use a Sun Stone, so I don't know if to keep it.
Should I ditch the Grass type and just move to a Bug/Poison type?
I would stick with grass types. As far as Petilil goes, it and it's evolution aren't bad at all. You get your first Sun Stone In Nimbasa City, where you fight the fourth gym leader.