[Greenskar]

You might as well get the 6" Bucky Cap. He looks amazing and should be much more affordable if you manage to grab him from Walmart or Target. Iron Man and Thor shouldn't be too difficult since they're out right now, unless you wanted classic versions of them. Widow will be difficult unless you pick up a Movie figure (assuming they do a 6" version of her).

Have you decided if you are going to do a Marvel Select Avengers or a Marvel Legends Avengers yet? All of these figures are probably cheaper in the Marvel Select line than Legends.

Edit: Here's some examples of what you can expect as a display if you go the Marvel Select route instead of the more expensive Legends route (note: these are not mine)