Okay I know the process:

• Make Fortify Alchemy equipments
  
• Equip them
  
• Make a Fority Enchanting potion
  
• Drink it
  
• Remove the equipments and equip them again
  
• Repeat 3-5, several times.

But when I do it, the bonus decreases instead of increasing. I made a Fortify Enchanting potion, the first time it was 20% stronger for 30 seconds. I drank it, removed my equipments with Fortify Alchemy and equipped them again. I made another Fortify Enchanting potion, but instead of being stronger, it's bonus was reduced to 12% for 30 seconds. I tried again by drinking it and repeating the process and my next potion's bonus was 11% only. Please someone tell me what I was doing wrong All my skills are at level 100 (thanks to Oghma Infinium exploit). Please help anyone as I'm playing in "Master Mode" and I seriously need better equipments BTW I don't have any patch installed.

You need to make and drink Fortify Restoration potion, not Fortify Enchanting potion.

THe ES wiki says that both Enchanting and Restoration potions does the thing. I'm confused

No, they do not do the same thing.

Master is a cakewalk. You need the Infinium glitch and the Fortify Resto? WTF?

Anyways you need fortify Restoration, not Enchanting.

And use UESP, not The Elder Scrolls wiki.

Fortify Enchantment is to make stronger Fortify Alchemy gear. Basically drink Fortify Enchanting, enchant some gear w/ Fortify Alchemy, put it on, make another Fortify Enchantment pot, drink it, enchant ANOTHER set of gear, equip the new gear, and so on. THAT'S the part drinking Fortify Enchantment is for.

Once you've got gear with a relatively high % on it for Fortify Alchemy (I think the normal cap is like 24%, iirc), put all that stuff on, then make a Fortify Restoration pot. Drink it, then unequip and re-equip your Fortify Alchemy gear. You'll see the percent go up from 24% to like, 29%. Make another Fortify Restoration pot, drink it, unequip/re-equip your gear, you'll see it's gone up again. For some reason, enchantments on gear are considered Restoration effects.

When you do this make sure you stop before you start hitting the negatives.

THIS