They are random. Just look at enchanted gloves. And remember, if you can find the enchanting boxes, you can rip the enchant from one piece of gear and put it on another. So if you find crappy gloves with the enchant, you can try it out first to see if you even want it. But if you find good gloves later on, when you find the enchanting boxes and have the gloves in your inventory, you can destroy the crappy gloves to get the enchant and then slap it on the better gloves.