I'd love to.
This is the basic way to accept an invitation to do something. Here's an example:
A: Would you like to join me for dinner?
B: I'd love to.
This phrase is a pretty traditional and slightly formal answer. A more casual (and less serious) answer would be:
Yeah, sure.
Another answer that falls somewhere between "I'd love to" and "Sure" is:
That would be great.
Follow PhraseMix