As the description says, what determines the %boosts my items will get when enchanting? is it my level?

I just learnt the "one handed do x% extra damage" enchantment. However im only level 31 in the skill and the boost it will give my ebony gauntlets is only 13%. How can I get this higher?
What impact will different type of soul gems have as well?

http://www.uesp.net/wiki/Skyrim:Enchanting