Porto - V.N. Gaia
I bought two extra copies of the base game when they were on sale at FFG and have never regretted it. I haven't done much yet with them, but I intend to give one to my son, and the other I've stripped the dice out (they have the engraved dice instead of the silkscreened dice).
I was thinking more about the extra tiles, I don't really know how the game plays but I guess that more tiles are better if I wanted to take a semi-rpg route and come up with campaigns for the game.