I would definitely not worry about gear until 80. The quest/instance items you get until ~78ish should be just fine, and then you can start work on some (all?) of the reputation grind for upgrades, and start running level 80 normal/heroic instances.

I only gem/enchant items pre-80 in order to get skillups or if I feel I need to boost the stats for one of my characters because it had been so long since they had gotten upgrades and are lacking in an area. I did make sure to enchant my shaman with new gems/enchants/etc because she had Kara/arena/ZA gear that would last her past level 75, possibly until 78. Anything that made the grind a bit quicker was good. I made the mistake of gemming/enchanting my hunter's gear at 70, and that was a badly wasted 1,500ish gold. He had replaced most of his stuff by 72/73.