Depending on how rich you our for T3 armour it depends. The basic and recommend if you dont like splashing out money on your armour is a set of "Pristine Forged Feyiron" which is cheap & quite effective, this will last you from 30 straight through to 40. Your next upgrade would be the Silvril armour which varies on level useage from 31-36, my character used silvril due to not having much money & i wanted to look different from the clones of feyiron, Silvril is not that expensive, ranges from 1g-7g on broker on my server (Highkeep). The stats our slightly better than Feyiron but you cannot imbue, that is your choice what you prefer. The next step up & best in T4 armour, is the "Pristine Forged Feysteel", this is a very hefty price, on my server per piece is sold for 50g. But the stats & mitigation on them our far superior to feyiron, if you have the money to spend on it, go for it. There is alternative ways of aquiring feysteel armor/weapons, just to mine in T4 zones such as Zek or Enchanted Lands, they our the rares, but will save you a hell of a lot of money. Basically you got the whole of T4 to go through so i would advise buying "Pristine Forged Feysteel" asap, to make sure it lasts the entire duration.