A book I might write

If I have the time, I am inclined to write a book called "The Club Players Guide to Gambits". The idea behind the book is to fill in the gap between when you sacrifice a pawn and when your game goes down the tubes when you opponent hangs on to it, and then swaps everything off for a boring endgame win.
I'm not really talking about proper gambits however (eg Kings Gambit) as the plan for White is pretty much mapped out already (hack away at f7). Instead it is the kind of mainline opening where one side can capture a pawn, and make it difficult for the other to get it back. In these circumstances the player who is material down should end up getting something for the pawn, otherwise the whole line is just bad. The book would try and address what that "something" is.
Here is game from the first round of the Aerosvit Tournament, where Van Wely does indeed take an offered pawn in the Gruenfeld, tries to hang on to it, but still gets beaten by Shirov.

Van Wely,L (2676) - Shirov,A (2740) [D87]
3rd Aerosvit Foros (1), 08.06.2008

1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.cxd5 Nxd5 5.e4 Nxc3 6.bxc3 Bg7 7.Bc4 c5 8.Ne2 Nc6 9.Be3 0-0 10.0-0 Na5 11.Bd3 b6 12.Rc1 e5 13.dxc5 White takes the extra pawn here 13. ... Be6 14.c4 bxc5 15.Bxc5 Bh6 16.Rc3 Re8 17.Ba3 Qc7 Black gangs up on it here 18.Qc2 Rab8 19.c5 Red8 20.c6 Rb6 21.Rb1 Rxc6 22.Rxc6 Nxc6 (D) And wins it back here.
23.Bc1 Bxc1 24.Rxc1 Qd6 25.Qxc6 Qxc6 26.Rxc6 Rxd3 27.f4 Bg4 28.Nc3 exf4 29.Nd5 Rd1+ 30.Kf2 Rd2+ 31.Kf1 Be2+ 32.Ke1 Rxa2 33.Nxf4 Bb5 34.Rc8+ Kg7 35.Rc7 Ra4 36.Ne6+ Kf6 37.Nc5 Ra2 38.g4 Re2+ 39.Kd1 Rxh2 40.g5+ Ke5 41.Rxf7 a5 0-1