Go to Draenor, make an enchanting hut in your Garrison, just craft the daily CD. There's no need to go back to previous times to raise your profession skills now. Everything can be caught up under "current content".
There aren't any enchants that require 700 enchanting. The only benefit is a higher yield from your daily cooldown. If you still want to get it to 700 for whatever reason, I'd do it purely from Draenor materials. There might be a few skill levels where older enchants might be cheaper, but you'd need to find a trainer/vendor with the recipe and get some appropriate gear (below ilvl 600) first.
As far Draenor enchants the cheapest would be to craft Enchanted Dust until you stop getting regular skill-ups (goes yellow at 50). Then craft your two daily crafts (secret and crystal) each day until you have enough secrets to get all the recipes. While doing that just enchant your own gear and maybe put up some enchants on the AH. I don't know how profitable it is right now, but I'd imagine the best profits are had with crafting the top tier enchants that require crystals. Those enchants are also the only ones that will help you get to 700, the lower level ones go yellow at 625 and gray at 630. Build an enchanting hut, assign a follower with enchanting and keep filling the work orders to get more crystals.