Anyone can answer this, how do you get sets and promos for the online game? I know that that is probably a stupid question . . .
Sets, Stash, Black Market: you buy them in store available after logging in to Goko (this is a two-step process, first you exchange real money into "Gokoins", then use those to buy cards, it's a bit less than $50 for all cards).
Walled Village, Envoy, Governor: you buy them for "Shields" that you earn by defeating adventures. To defeat the later stages you need "Zaps" which you buy in the store. You can buy those for RL, but also for "Gold coins" you earn for playing games (if you play multiplayer or bots a lot, you will have thousands of those coins, so definitely you should not buy "Zaps" for RL cash). "Shields" can be also spent on Stash or Black Market, but it's not recommended because other 3 promos can't be bought with money and there's only enough adventures to buy 3 promos.