Each rank with the gunsmith, up to rank 3, get you a differnt perk roll with each gun you order. Maximum amount of guns you can order at a time is dependent on rank. Each wensday you will get your weapon from the previous week (order one today, receive your weapon next week). If you have diffculty choosing a gun for your play style, I highly suggest you go on youtube and go to Planet Destiny's youtube because they go over each perk roll for each order every week to see which one suits a pve or pvp player.