let's say i want to put 60% frost protection on my gauntlets, 30% fire on my boots and 30% shock on my helmet. i would have to find parts of my armor with those particular magic resistant enchants? to be able to enchant my armor?
There are others more knowledgable in the process than I, but, from my experience, once you have the enchantment (in whatever level - it can be lower and as your skill increases the % will go up), the only limitation to what you can put it on is that armor to armor/weapon to weapon, etc... In other words, if you disenchant an axe with frost damage/stamina damage, you can then use that to enchant any other weapon you have; if you disenchant armor, then you can use it to enchant any other type of armor (of course there are limitations on that: you wouldn't be able to put an archery enchantment on a chestpiece, but you could on a helmet, gauntlets, gloves or boots if you wanted).
Important to remember that the % you are able to enchant will change over time as you point up in the skill and get the perks as well as if you are using enhancements (potions, gloves, circlets, spells, etc...) when you are doing enchantments.
An example I have is that: I disenchanted a sword with fire damage bonuses that were +30. Initially I could only enchant a new item (a bow in this case) to +8, then, as I got more points to +14, then, when I got higher +20 and eventually the full +30. Now I can go higher as I have the +25% perk on fire and also have both gauntlets & a circlet of +25 & +10 respectively. Now I can enchant the fire damage up to +50 and I would guess it will go higher still if I also used enchanting enhancement potions. Particulary with armor I like to use a black soul gem or the dark star as it raises the %ages, although, with weapons they are good too because it gives them more charges before needing recharged.
It's really a matter of trial and error, as with alchemy and smithing as to what works best for you.
Currently, on enchantment I am working on getting the double enchantment perk to mix things up (want soul steal and fire on the same bow).
Hope this helps, but, as I said, I may not be totally correct as there are so many other folks that are so much more experienced than I.