i'm not a fan of giving pets as gifts either, especially bettas since a lot of people assume that having a betta = not having to take care of it. i would ask if they're interested first, and if they are, then educate them on keeping a betta and then offer to buy them what they need.
one of my bettas is a rescue from an ex friend who got him as a gift, and didn't take care of him properly. she asked me if i wanted her fish and i said sure, but when I saw him i was appalled..he was so pale and had fungus..all she had him in was a vase!!