Here is an idea for a card game I have worked on a couple years back.
Its based off of the Dragon Warrior Monsters games, but kinda plays like Yugioh/Pokemon. The basic idea of it is that you can use these cards to summon monsters to fight your opponent and your opponent can do the same. You can also fuse monsters together to make stronger ones (the fusion works the same way as DWM in that each monster has a main type and subtype)
There are also different types of cards such as Item cards / Field Cards / Equipment cards as so on. Battles are like a mini rpg game in that you start out as level 1 and as you beat these monsters you level up.
Here is a sample card a friend made for me.
And here is a draft of about 300 monster cards (most of the names are kinda silly looking back) and their rarities. Unfortunately I’m not an artist so I can’t code this game myself.