The short answer
Snapshot does not offer gift cards, e-gift cards, or gift certificates, and there is no store credit to purchase. Every order is a specific printed product paid for at checkout.
How to give a card as a gift anyway
The simplest route is to make the card yourself. If you have a good photo of the athlete, you can build the card, preview it, and order it shipped to any US address at checkout. That works for a surprise.
If you would rather the recipient choose their own template and photo, build it with them. Designing is free and needs no account, so they can experiment until it is right, and you place the order. This is how many parents and grandparents handle it.
For a whole team
If the gift is for a team, a coach can set up a team page and share a link; each family orders and pays for their own player's pack, so nobody needs to hand out credit. A Rookie Box holding one card per player, ordered by one organizer, is the other route.