Taking your age into account I would vote for a corn. They are a great first snake and a good choice for a younger keeper that will not have you buying to much gear.
Also make sure you are ready to care for a snake as many can live a very long time. Much longer than most cats and dogs. You are going to have many life changes over the next several years and it is all to common to see a free snake being offered by parents that were left with their kids pet when they went off to college.
Make sure you are really ready for it.