With you current desired perma-members your team is weak to: Poison, Ground, Flying, Psychic
And overall lacks resistances against: Normal, Poison, Psychic, Rock, Ghost and Fairy
Note: Your weakness to Ground and Flying in this case means that you have more mons that are weak to it than resist it, so it's not that critical.
The easiest fix for the unresisted types would be Steel as that would only leave Ghost unresisted, though from your box pictures I take that's currently not an option. Sandygast with its Ground/Ghost typing would take care of Normal, Rock and Poison so