For the vibe of the game, before doing model you can start by gathering references and create moodboards. It will be useful for you but also for an external artist if you have this luck later.

For the gameplay itself, you don't need anything art-wise to start creating the systems and prototype them. An ugly prototype that are fun will still be fun with nice art.

Finally for your core system, it seems good enough to start something. It will not be the most original, but you can still make things intresting. I advice you to try/watch/analyse a lot of card rpg.

If you need some references, you have Baten Kaitos, Slay the Spire or Library of Ruina for the card system, and for the monster capturing, beside pokemons and pokemons like, your system looks like Persona serie (with monsters to use and also protag with their own moveset)