From what I remember of the Maxroll guide:
I started upgrading as soon as I got to WT3 after completing the campaign at around 51. Taking off and applying aspects is cheap enough once Legos start dropping regularly in WT3. Be aware, you can only take off and apply the aspect once, so if you get a perfect roll, you may want to keep it till 60+. AFAIK, item level is secondary to stats/high rolls on everything but weapons.
Enchanting is the big cost, and it's probably best to wait until WT4 for that, or at least 60+.
Maxroll guide also recommended to start selling, instead of DEing, all blues and yellows (unless the yellow was Sacred), when getting to WT3. I would dump all sacred into the last bank tab, then evaluate them in batches once the tab was full, selling any that I didn't want to use.