Another game you might want to take a look at is Dominion. You buy a single box with the cards for all the players (from 2 to 4 IIRC) so no need to buy extra decks.
I enjoyed Dominion, and generally appreciate games where you don't have to keep buying things to play competitively. I've never actually played it, but I was always intererested in Codex: http://sirlingames.com/codex
It's modeled after real time strategy games (Warcraft 3 especially), and was designed by David Sirlin. Sirlin writes about game design, and I've really enjoyed his commentary on competitive systems. He did the rebalancing for Super Street Fighter 2 HD Remix, and the changes he made are discussed in a series of articles here: http://www.sirlin.net/articles/sf
You can various other articles he's written by clicking around that site.
I was interested in Codex but at the same time I played Fantasy Strike for a hot minute and it kinda cooled me on Sirlin-as-designer rather than Sirlin-as-analyst. I'd be interested in whether anybody has played Codex and enjoyed it.
You really need at least one expansion (and make it Intrigue) before too long to keep the game interesting. IIRC the base game originally had the first 2 or 3 expansions but broke them out to cut the costs down (and for the expansion revenue later.) IMHO get them all up to and including Hinterlands at the least if you get into it.
Intrigue is good but you have to have a consistent playerbase to start rolling that stuff into the game. But I find that the base game is pretty intuitive and somebody can play competitively even on their first play-through.
I'd bet the overwhelming majority of Dominion games are not just using the base set, but the "recommended first play" card selection.
It's modeled after real time strategy games (Warcraft 3 especially), and was designed by David Sirlin. Sirlin writes about game design, and I've really enjoyed his commentary on competitive systems. He did the rebalancing for Super Street Fighter 2 HD Remix, and the changes he made are discussed in a series of articles here: http://www.sirlin.net/articles/sf
You can various other articles he's written by clicking around that site.