Ghost/Dark Team

I’m currently on my first playthrough, three badges in on the ‘Dark’ storyline, just before going to the whirl islands to confront the abyssal leader. I think it’s important to note that I’m playing on hard mode and up until now I’ve been repeating a cycle of being underleveled for story missions, losing the fights to set up that I wasn’t expecting out of an ai trainer, and then having to level my team up to a couple levels higher than the story enemy im currently stuck on in order to progress.

Right now, I’m looking to redo my team with a dark/ghost/psychic theming. My current mons that fit the category are as follows:

Delta Charizard
Delta Roserade

I’m super open to any suggestions that I should pick up/strats I could use to get the set-ups that im kinda lacking on.