A day ago or so I made a thread about Master Yi tips and such, But turns out i'm not very good with him. So whats a good easy to learn how to use champion for a beginner?

Cause I'm tired of always being the total noob on the team :P

Ashe is pretty easy, just have to be careful to run at the right times.
Get a meki pendant to start, then boots (helps with running away), and then go for nothing but attack damage or crit chance.
You don't really have to think about item build much, just go nuts.

What should I put my masteries into for her?

whatever. Probably all damage and mana regen.
I use teleport/ghost/flash plus heal/ignite for summoner spells.

Oh, how bout runes?