This is a MF build I always use, and it never let's me down. The most important thing to do is just press W and right click to kill.

You can change anything you want in this build. But to me, this is how I like it. You can change the runes into mp5, but I don't like those for 2 reasons. First is that W skill is the most important skill in this build, and it doesn't waste to much mana, and second is that I get blue buff whenever possible, if we have a jungler, it's the enemy blue buff, if they have a jungler, my jungler helps me counter theirs. Masteries are your choice , you can go Defensive a little instead of Utility. As for items I wouldn't change them, because this build is concetrated on W and auto attack. I'd suggest last hit as much as possible, harras as much as possible and stay out of fights, be the pearson that is getting ignored while you deal all of the dmg.

I'd suggest, if you wanna change, to always have Flash, and the second spell is ur choice, since MF has her own secret ghost as passive.

I never take mid lane as MF, always farm sidelane. I like sidelane more because :
1. I can kill the enemys my teammate and I already harrased, so instead of farming 1 guy that can't play, why not farm 2.
2. Easier to last hit, and don't have to worry to b when I get the gold.

If you read all, I got nothing to say, try to get Jungle monsters if you have no jungler, bonus gold is always welcome, take care of ur self, and if you see u will die and can't run, press that W and own some noobs.