I just wanted to reply to this thread to give my perspective.
I just wanted to share my progress. I have been playing the Adventures for about four months now, since joining Goko, in an effort to beat them all, claim all the promos, and finish each level of each "territory". I'm a bit of a completist, I guess you could say.
In the last four months I have advanced through the adventures in:
Base Set 1, 2, 3
Intrigue 1, 2, 3
Seaside 1, 2, 3
Alchemy 1
Prosperity 1 (working on 2)
I have managed this solely by spending the coins I collect from playing and winning games on zaps. I do not spend zaps to raise my hand above what a normal Dominion hand should be, nor do I zap my opponents below what a normal Dominion hand is supposed to be. Although, in annoying cases where I get stuck with four Estates, which has become more and more common in Acts 2 and 3 of each territory, since I cannot zap the fourth Estate into a Copper and get rid of the disadvantage that places me in, I do zap two of my remaining six Coppers to Silvers.
I typically buy the zaps 10 at a time, for 70 coins, because the rewards for buying Zaps in higher bulk amounts are negligible (something like three extra zaps for waiting five times as long). When I do not have 70 coins to buy 10 Zaps, I go to play Multiplayer or Play Bots until I earn 70 coins, which I promptly spend on 10 zaps and return to Adventures. Aside from these games, I do not Venture away from Adventures. (pun intended)
In four months I have played 1,082 games of Dominion and amassed a record of 592-466-24 (.558), I have earned exactly one promo card, and am about to earn a second one.
My response to this is that I'm aggravated that it has taken this much effort to make progress this slowly, but not so aggravated that I refuse to stop in my mission. However, while I am willing to grind this out, day by day, and eventually earn the promos, I can imagine that a vast majority of players would not be up for this task.
One last thing. The completist that I am, I am also really peeved, after the amount of effort I've put in and plan on putting in, that I'm not going to be able to get Walled Village without paying for it, since I did not link this account to Google upon starting it.
I'm not trying to make any arguments with this post, only give some perspective to the community.