Della and Jim are poor. Really poor. They cannot afford to buy each other gifts for Christmas because putting food on the table is more important. In order to afford a gift for each other, Della and Jim (independently) sell their most prized possession to get money for the gift. Jim sells his watch. Della sells her beautiful hair. Della's gift to Jim is a chain for his watch (which he just sold). Jim's gift to Della is a set of combs that she wants for her hair (which she just sold).
Yes, his gift was suitable. Jim knows that Della's hair is beautiful, and he knows that she takes great pride in it too. The combs are a perfect gift, because Jim knows that Della will love putting them in her hair to even further enhance its beauty. The gift is both thoughtful and long lasting.