I love the concept but I feel like you can get very unlucky in this game. If you get lot's of low paying common cards without synergies, the prices grow way faster than your income and you can only dream of buying cards from the shop.
So for rebalancing, I'd suggest to make the price growth a little less punishing.
Maybe even give an option to restart a run without prestiging, just to not get softlocked behind ever growing prices.
As for when the game get's boring, I'd like a goal to work towards. I have some ideas:
- simple achievments for income/s and stuff like that, giving small rewards
- challenges, for example reaching a specific income/s with only using nature cards and as reward a small global multiplier to all nature cards, like + 0.02 or something, stacking with more and more challenges.
- you could also add stuff like investing into building/building a town. This could become more or less complex, either the buildings need just money or different recources. You could make it so nature cards give a bit of wood, beast cards a bit of meat, earth cards a bit of stone, arcane cards a bit of mana, etc.... Then you can use these recources. New buildings could unlock new cards or passive bonuses. There is a lot I could think of.
- I could think of a way to rework the prestige mechanic. For example, if you'd lock more powerful cards (legendaries and stuff) behind other content like the above mentioned, you could make it so you don't lose all your cards on prestige. Maybe reset them to lvl 1 or lose all cards except commons. Then you can build a building to also keep uncommons and so on.