The game progression at first can be a bit confusing, this should help:
There are 3 heroes available, each with 2 decks, negotation and battle decks.
Three modes: story mode (normal), story (easy) and brawl (less focused on story and characters, and more being a bounty hunter taking random jobs during five days). Brawl unlocks after finishing the story mode, it reuses content of the story mode too, but it’s there to not bore the player telling the same story dialogue he had read several times.
Progress during the duration of the run
-New cards can be bought, obtained as rewards, etc
-They can be removed too by some npcs or random events
-Cards have a xp level, after use can be ugpraded (for the duration of the run)
-Items can be bought (powerful cards with 3 uses, they are destroyed after that).
-Grafts, they are similar to the random items from STS, they apply boons to the card combat. You have a maximum slot number for them, which can be upgraded too, but at a hp cost.
-Graft can be upgraded with xp once, like cards.
-Every character in the game has a social boon, a social bane and a death loot. The social boons are passive positive effects, like ‘at the start of each battle gain 2 temporary power’ or ‘once a day, you can ask a member of this faction to help you out’, and they are gained if you get a character to love you. Social banes are negative effects, gained if someone hates you. Death loot is a card gained if you kill them.
-Your reputation also can give your new cards, for example when you kill several people you will get a card about it.
-You can gain pets, which serve as ally in both combat systems, and can be upgraded (trained) too.
Metaprogression
-Successive runs unlock cards permanently for that hero as card sets. Card sets can be toggled on/off but then you are in a custom game where you can’t progress the Prestige.
-Unlock perks, maximum of 3 active perks to choose for a new run, from a list of 40.
-Perk points are obtained by ‘grifts’, in game challenges like ‘doing x damage’ or ‘gaining x gold’ or ‘winning x battles’. Common to the three heroes.
-Mettle, a rare currency obtained in game (and can be used ingame too) to that improves each hero slightly, but the upgrades are permanent. Upgrades aren’t super big but unlike perks, there is no limit with active slots.
-Once you finish a game, you unlock the prestige mode, to increase difficulty Prestige - Griftlands Wiki
-The game also has a system of mutators for custom games Mutators - Griftlands Wiki You have to finish the game first once.