I tried to do these "ultimate weapon/armor" (that ones you see on youtube that armor rating and damage goes over thousands) following this:

elderscrolls (dot) wikia (dot) com/wiki/Alchemy_Tips#Advanced_Alchemy-Enchanting-Smithing_Power-Crafting
Along with this:
youtube (dot) com/watch?v=71Aev5sZxa4
The problem is, even using all the pretty badass set that goes over a million with 'fortify enchanting' or 'fortify smithing', some enchantments don't seem like having any effect (for example, fortify alchemy and fortify smithing enchantments are only going to 1% or 4%) and when wearing the smithing set and trying to improve weapon or armor, it kinda 'block' from being able to improve (just like when you don't have the improving material), then if I try to craft anyway, it says 'you lack the required skill' or something like that.
Please help! Don't tell me I did all this for nothing

There is an armor "cap" in the game, which is 567 if you wear four pieces of armor. There is a hidden AR of 100 for a full set of armor so if you wear no armor you need a displayed AR of 667 to be at the cap. Increasing your AR above this cap provides no additional protection.

This isn't entirely true, though it's not entirely false either.

Some enemies can ignore a portion of your armor score (See: Bone-Breaker and Skull Crusher perks) so numbers above 567 can help, though these instances are extremely few and far between. (Usually only boss monsters, namely Mace-wielding chiefs, and two of the new Dragonborn enemies)

Even with an armor rating of 1000 though, a maxed out "Bone-breaker" Perk would reduce that to 250. To "Truly" Max armor, You'd need 2668 armor. There are new powers and abilities (Dragonskin from Vanilla, and Earth Stone boon from Dragonborn) that increase your raw damage resistance, which should be all you need for these rare encounters.

It's probably worth adding, that you can also "Raise" The defense cap by using armor spells in addition to armor itself, but the maximum cap is 85% if I recall correctly.