Welcome!

One of the quickest ways to grow is to rent some cards. I do this via peak monsters (and wrote a little article about it a while ago : @sbenbow/renting-cards-best-thing-i-have-done-newbie).

The interface has now changed on peakmonsters, but it's still quite intuative. If you are unsure, start small and rent a few basic cards for a couple of days. You probably won't even break the 1 DEC mark doing this, but the increase in win rates will earn you more DEC than that.

Then it just spirals. As you progress up through leagues you win more DEC and more of your own cards. You can then start building your own base deck up - but also rent the higher level cards that you want too.

By mid-season I tend to get to the Silver levels and start earning 15-20 DEC per match, and getting three cards per daily quest completed.