Sorry, it's not possible to upgrade regular equipment from one level to another, but there are certain types of gear where you can. For example, Savage gear (lvl 40) can be upgraded to Slayer gear (lvl 80) later in the game--which can be made at General Krahn in Starglade using PvP badges.
You can also forge many types of gear using Synthesis in your item menu--if you have enough shards and are lucky. These can be class and level specific, so pay attention before you make something you can't use! Hope this helps.