I'd say Haunter, Ivysaur, and Golbat are givens. After that choices get pretty slim, though Skorupi, Tentacool, and Stunky are pretty decent; after that Croagunk, Roselia, Nidorin@ are all that's left usable.
As for your two non-poisons, you'll need two things that can take Psychic attacks well. I'd say Metang or Magneton for one. Seadra is a solid choice offensively, or Rhydon for a Physical tank. Duskclops is pretty good as well. Gligar again is a solid choice for both offense and defense, plus it's quick. Well, before I go on with the deveolping patter, take advantage of pokemon that got an evolution (despite not really needing one).