In outland as has been said the first 5 quests will get you changing your armour fast anyway , do not buy anything after you are level 50 as at 58 you can get to Outland and i guarantee you will change all your armour within 2 levels , if not by quest rewards it will be on drops , for example those birds in hellfire for me were dropping greens of all types like i was on a shopping trip , something like 1 in 5 drops were greens , so to buy anything would be crazy .
For example i thought as you did and made sure ? i was ready for Outland , i spent a small fortune only to find within an hour i had changed 4 pieces of my armour and after about 3 hours had a decent weapon upgrade as well as a full change of armour , so just get out there and have fun killing everything you see ( before it kills you ) i can guarantee you will change even blue pieces for greens in Outland.
Also in Outland everything is worth more , it may not sell at auction but it vendors for crazy prices anyway , even the trash stuff can be worth gold.