The base idea is nice but it would be good to add more elemtents into the gameplay like upgrades during the run, traps, monsters that are weak to different attacks like sword deals more than magic and vice versa. Actual use for the gold except score would also be a good addition to the gameplay. Maybe have a variation of the layout of cards not always the same 3-3-3 and random mini boss encounters depending on the score or floor could also add a interesting twist to the game. A leaderboard could be a optional addition for people that like to be more competive or to track personal progress. Trophies are also a option that could work well for that game concept e.g. clear 10 floors without using spells.