i know he use whatever i give him .
but whats the best armor for Marcurio ? best weapons and enchants ?

Below is some info on followers, and a website that provides a lot of info on followers, including a Google spreadsheet that should answer your quest, I hope.

A follower's level can continue to increase along with the player's level, whether they travel with you or not. However, each follower has a maximum level (which varies for each follower). Also, each follower has a specific set of favored skills. Regardless of how often a follower uses a skill, they do not get better at it, as a player does by continuous use of a particular skill. For example, trying to force Brelyna Maryon to be a sword wielding, shield bashing warrior will not work, she will always be more adept to using magic.


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

Good luck.