If you are beginner, then just play for clintz until you have decent deck.
Can you score over the 1/3rd in DT? - Yes? Play full hours to get credits, credits = cards = clintz. If you cant get to 1/3rd then play 1 game and then something else.
Can you manage yourself in DM to position to top 3 regulary ? Yes? Play DM while not playing DT.
Can you manage yourself in Survior to strech to 5+ wins every now and then? - Then do Survivor instead of DM while not doing DT.
Play ELO to your maximum potential, but dont bother with it seriously if you cannot progress. ELO = credits = cards = clintz.
When possible upgrade your deck. Dont bother to save big pile of money, you will get the bigger pile lot easier if you have good deck than to struggle with below par deck. You should spend your first 20000 clintz to your deck. Eventually wins pay this money back.
... Then there is the market and the marketplay. That is huge source of money to those who can, and those who cant are the source of that money...