Porbably not the best explanation of it , but here it is :
In Circadian Dice basically you choose a class (you unlock more of them as you play) and try to complete several levels that are made of a succession of enemies waves , sometime bosses. More levels will appear progressively atfer you beat some of them.
Each waves, you have a certain amount of re-roll, and you roll 2 die (at first), you gain experience due to various factors (killing enemies, buying die faces in the shop, abilities, etc..) and each 2 levelup you gain an additional die (and its faces).
Each die have very different faces (the game has truckload of different die faces that each have different effects) that are given half at random half depending on your class , so with the rolling results you"re trying to destroy the enemies in each waves to progress further.
You can gain gold (from some face, from abilities, from some specific enemies, from some specific chest that can sometime be dropped by an enemy, etc...) and you can use that gold to buy new faces when available in the shops (or not as gold gives score bonus in the end), price can vary depending on how powerfull those faces can be. You can also reroll the shop offering, but after a free reroll, they cost more gold
Then there are abilities, that consume each some specific type of mana (that you can refill when rolling a face of that specific type) and can influence a lot of what is happening, then there are items (most you'll have to unlock by completeling levels and gaining stars depending on how high the end score is) that also will influence a lot of what happens in many ways (depending on the items).
Basically it's a game based on luck, decisions, choice between risk or cautious to balance the randomness making it extremely replayable and addicting.
edit : managed to finally unlock the last item of the monk (on normal mode)
I was missing 3 stars and had too hard time to complete higher levels, so i went back to the Necromancer Tower that i had completed with the monk but couldn't get more than 1 star, and this time managed to complete it with 4 (the Dreamsaver item helped a lot there, it gives score points whatever bonus choice you take between waves, but it does not add streaks so you may still want to pick score a couple of time for better scoring)