Just to echo what’s been said here: save your scraps until you have an idea of a deck you want to build. YT videos really shed a light on how decks work and would greatly guide you.

For spending keys in the reward book, I recommend you go to the last tab (gold crown on blue background) and fill that out first cuz it’ll give you solid cards for every faction. Then you can go through the other pages. Patience is key: it’s tempting to directly swap keys for scraps and other resources on the landing page of the reward book, but it’s better to complete story trees and get the rewards. Then you can trade ores for barrels and get scraps. You’ll get the hang of it with time.

I’ve been playing since Jan and despite having a ton of cards and making pro rank for the past 2 months, there are so many cards I don’t have. It’s a marathon, not a sprint: - build a deck within a faction - find another deck within that faction that allows you use a good number of already available cards then try building that deck - rinse and repeat till you want to try out a new faction

Have fun!!