Gold!
Gold is the currency of the Far Wilds. You can gain gold in many different ways. The easiest way is to purchase it from the Market tab.
The true cost of packs
Packs cost 150 gold. This might seem like a lot to spend for only 15 cards but keep in mind that there is an active marketplace where you can easily sell the cards you get in the pack that you are not interested in. In fact, about half the packs you buy you can sell them back on the market for more than 150 gold. So really you should consider the gold you spend on packs as an investment that you can turn back into gold whenever you need to.
Another important thing to keep in mind is that once you have cards in your collection they are yours to do with what you will. You can sell them for real money on ebay, barter them for a chicken, or anything you could do with a physical card you own.
And if you still think it is too much check out Drafting and Leagues below. Those can get the average price per pack down to 90 gold.
How much does it cost to build your own deck?
Cards have a wide range of values anywhere from 2 to 200 or more gold. The price of a card depends on a lot of things but most of all on the card's rarity. Rare cards aren't necessarily better than common cards but they do cost a lot more. So if you build your army the right way and avoid the more expensive cards you can build a competitive Army for less than $3.
Using Gold to Draft
Drafts are not only fun but a great way to stretch your coin. You can join a Keep Cards Draft for 500 gold. You are getting 450 gold worth of cards and the chance to to win all your gold plus some back. The average prize from the draft is 180 gold. This means packs from drafting only cost about 107 gold. And if you are an above average player you should be able to draft on your first entry fee forever.
Using Gold for Leagues
Leagues are another good way to get more bang for your buck. The Domain League gives you 3 packs of your chosen domain. The average prize varies depending on the number of people in the league from 68-230 gold. Leagues under 25 people actually payout better than drafts. The only drawback is you can complete a draft in an hour while a League will take several weeks.