This is really dependent on
- which gambit
- the style of play you prefer.
For 1, consider the King's Gambit. The theoretically preferred line for Blacktheoretically preferred line for Black is 1. e4 e5 2. f4 exf4 3. Nf3 d5! which immediately returns the pawn. On the other hand, in the main lines of the Benkö gambit, White holds a pawn advantage well into the late middlegame.
As for 2, I'm usually fine with having a material advantage, defending against an attack, simplifying and winning in the endgame. Other people like having the initiative and will usually try to return the gambited pawn in exchange for a (counter)attack.