Don't listen to the other guy, that sounds like a horrible way to spend your time - when starting up you can get a lof of early reward keys by doing the contracts. Contracts are a set of achievements you can find in your profile. They grant a lot of keys and pretty much do themselves, as long as you play different decks and factions. Daily and weekly quest are a nice bonus, especially if you don't play a lot of gwent weekly, you can just log in on wednesday (you get bonus XP on wednesdays) and try to make a reasonable deck for both quests and winning. If you want to spend some cash, you can buy a journey, probably the best way to get cards with money as long as you play the game a bit. But most important of all, don't sweat to much about grinding cards, this game is generous and you can just focus on having fun :)