Am I Obligated to Give a Gift?

I recently received a wedding invitation from an old friend that I see sometimes, but no longer talk to. I had known that they were getting married for some time (we still have a lot of common friends), but I had assumed that we were not invited to the wedding.

I am sure that C, my husband, and I are on the "B list" or maybe the "C list" since we didn't get a save the date (the couple sent out an electronic save the date) and we just got the invitation (most of my friends received invitations much earlier) with a reply request of only one week.

C and I are definitely not going to the wedding since we will be attending another wedding the same weekend in a different geographical location. What I'm struggling with is whether we should get the couple a gift.

I wrote this post a few days ago. Since then, I've decided to buy them a gift.