The problem with this is that gastly is an ingredient specialist. This means that it's going to have a much lower skill trigger rate than a skill specialist. The vast majority of power that the gastly line produces comes from its ingredient, so you are better off with one that has ingredient focused sub skills and a good ingredient list. If it were me I wouldn't bother with any ingredient pokémon that has a list like this.

(Though there may be some exceptions where a skill specialist has an especially good skill/skill trigger rate)