I would wait until reaching Lions Arch before upgrading your armor. That should see you through until the desert. Its also worth getting collectors armour if you can, saves on cash and is just as good. That way you can save your cash until you reach Droknars Forge where you can get the maximum defence armor in the Game
However, do you only have the prophicies chapter? If you have bought Factions and added it to your account, from Lions Arch you can visit Kaining Centre and get max armor from there.
I would seriously suggest visiting
www.guildwiki.org and searching on armor for your proffesion. It will show you all the different art sets, what is required to make it and where you can get them
One last word, if possible buy crafting supplies for armor via other players, rather than material traders as that will save you a packet. And don't forget that armor is customised for you, so buying armor from other people is not possible
Good Luck!