Miss Fortune. I like her. She has a great base attackspeed and movement speed, especially thanks to strut. I have played a lot with Ryze, but it's annoying you are always the main focus of the opponents due to the fact you start with only 490 HP.

You need to get feeded with many champions, but with Miss Fortune it's no extra need. You just farm a lot of minions, get some gold and stack your AD and AS. Movement speed with berserker graves and you're done.

In first levels (for support) you can best get Make it Rain (E). Build up W and E spells till lvl6. At 6 ofcourse your ulti (check skill setup).
Slowly build up double-up, because I think it's more useless then usefull (maybe last attack). With Unpure shots you gain AS and slow the enemy + it's healing. Ultimate with make it rain. Put E spell behind them so they can't go back that fast and push with W spell. Final attack is your Q and then maybe when a teammate can slow them use Ulti. Don't use your ulti to quick!

In loosing battle 3v3.
Sometimes, your team is not so great. And when the enemy has broken your turrets on one lane AND the inhibitor? You're screwed. WRONG! If you can time your spells with your teammates (like Evelyn on AP with her stun) you can seriously get the ace (trip). And yes, then you need to push

Farming up.
Don't be afraid to loose mana,, you can recall and walk back soon enough. When your AD is arround 140 and AS round 1.200 get some minions. Make it rain upon them (make sure you hit enough). Then Impure shots and get 10 minions in 3 seconds. Getting some gold and get your items!

Use make it rain on minions in the beginning. Gaining gold is important, as you first need AS and AD with miss fortune.
If you know your team will need you a lot (bcuz MF is carry), get ghost with exhaust. Otherwise get ignite instead of ghost.
Sometimes with 5v5 midbattle, don't show yourself right away. Get in sidelane bush and wait for them to come. When 2/3 with half HP coming, drop Make It Rain in bush, step back a bit and go for it with the ultimate ulti!

Winning garanteed