And box of Sees Candies is my go-to gift when I buy for someone I don't know that well and working with a budget. Also, we have a small chain of high-end movie theaters here - you can order real food, wine, micro-brews etc. I often give gift certs from there if it's a couple that likely wouldn't/couldn't spend extra for a nice evening out - still a reasonable cost for me. I guess I usually try to aim for some sort of treat that a person isn't likely to buy for themselves.
What does this couple like to do, to read? Find out what their interests are, and look for gifts in that category. If he's a DIY'er, get him a gift card to HD or Lowe's. If she likes to cook, perhaps a gift card to a reasonably priced cooking business.
Or is there something they can use for their home?
Or is there something they can use for their home?