[cellardoor]

So long as you can pick and choose then you'll be fine.
If you can grab Moudular Iron Man, the Modern Thor, a Bucky from the cap line and a Steve Rodgers figure then that's the modern Avengers. They look great together.

But then you've got to have spiderman, Wolverine and Thing in there as well.

And Red Hulk, don't forget him.

Oh, Ms Marvel in her modern costume and Jessica Drew Spiderwoman.

And a Hawkeye.

Oh, and Iron Fist and Luke Cage.

But then you're done.

Unless you want x-men figures as well. There's a few of those (Madrox, Kitty, Colussus, Iceman, Many Wolverine's, 4 or 5 Cyclops, the comic pack Phoenix, Nightcrawler, Warpath...and a few more.)

After you've got all those you're done though...until the next wave with other x-men turns up.
But then you're definitely finished.
Oh, a Sentinel you say?
More waves? More Comic packs? More superhero sets?

Seriously though, you're doomed! It doesn't have to cost a lot...but it will!
Enjoy!