Grim Quest and Grim Tides. Two games by the same person. I haven’t played Grim tides yet, but it’s also free. Grim Quest is not a particularly large game, but I’ve still managed to play it over many years. I did a full run of each difficulty one by one. There is a bit to learn before it feels easy and casual, but it does get there. To be fair, I try to play it without dying. If I let myself die, it would be alot more casual even from the start. Dying is not heavily penalized on default settings, but you can alternately choose to play hardcore. Otherwise dying usually just means you gained less money for that run, and didn’t make the game any harder. The game only gets harder when you successfully clear a dungeon. You can also just exit the unfinished dungeon without dying and keep most of what you have acquired so far on that run, minus a small fee for quitting the dungeon.
There are preset difficulty options, but you can also craft your own custom difficulty. There are things you could spend money on, I think it may have started out with ads. But I consider games with ads that you can pay to get rid of as basically a free demo, and getting rid of ads is the purchase price if you like the game. So they don’t deter me if they don’t basically break the game to add ads to it, or affect the flow of the game whether the ads are there or not.