I need counsel that I will probably not heed and do whatever I want instead.
I recently moved to another city and left my board game collection very behind. I found a board game shop in my new city that sells Adventures, but not the Base Cards. I already own Intrigue, but not the Base Set. I could buy the Base Set and Adventures (expensive!). Or I could buy Adventures and order the Base Cards online, and maybe buy some other box when I have the money (Guilds or Dark Ages).
What do you recommend? "You know you are going to buy them all eventually" is not an answer.
If you ask the local store to order the base set, then you can support the store and possibly encourage it to order an extra set to put on the shelves. It might be enticed to carry more Dominion, which means more players. And hey, if you bring your Dominion to the store for game nights, then you're going to make a few converts.
But it is usually cheaper to go online, and I respect that. I often buy online too, but I do try to support the local stores in some instances.
You say you're not impressed by the base set; I can see where you're coming from. After all, one danger of expansions is that they become more and more interesting, but keep in mind that you would likely be sprinkling base cards in there. If all 10 kingdom cards were from the base set, then I could see it looking kind of bland. On the other hand, some Adventures cards mixed in with the occasional Smithy or Witch or Throne Room can still be pretty exciting.