Well you can get free cards by doing missions. Leveling up with complete leader missions for you which at level 15 can get you hugo which can greatly improve many decks. Other mission has a random chance of giving you a random common uncommon or rare card based on the gift size of the mission (I believe that is how it works).
There are a few ways to make money quicker and that to play Tournament, ELO, and Survivor.
Tournament is usually the best way to go about getting money. A cheap montana deck with Hugo can win about 500-1000 clintz if you put in the solid hour. A tournament gives an extra 50 Clintz for just play a single match, 1 credit if you reach top 1/3 (you need generally about 100 points), and you get more money if you reach the top 100. It isn't that hard to reach top 100 due to a lot of players most just playing one match for the 50 clintz.
ELO is a bit harder to make money on unless you a top player in the game but it gives out credits easily. Just playing 5 ELO matches a week and having above 1000 ELO points gives you 2 credits and 12000 points give 5 credits.
Survivor is a great way to make money for a newbie. You get an extra 5 clintz each battle you win (which increases every few time you win in a row) and you will face opponent that are at a disadvantage due to lower pillz. If you get extremely lucky can get a got 10 wins in a row your looking at free 648 clintz.