Some people prefer flat AD runes as reds. Only do that if youre missing too many CS otherwise. Yes, it makes Lasthitting a bit easier, but you will do far less damage with ur Q and autoattacks to your opponents, epeccially after getting your early BF Sword.
I personally found it pretty easy to lasthit with Miss Fortune, since she has a bit of extra damage on her w passive.

Reasons for this skill order: w is a very strong lvl 1 skill that makes you lasthit easier. its much better in skirmish level 1 fights than other skills because it does alot more dmg over time. no other ad can contineously trade with you or they will die, assuming both supports are doing the same and you dont take too much minion agro.
her Q should be maxed first because it does insane dmg and with its bounce it can give you safe poke. you should always try q the caster minion backline when either opponent ad carry or their support is standing behind them. q is even better than the autoattack reset from vayne because you can do it between autoattacks and it gives enourmous amounts of extra burst.
w should be maxed secondly, even though you start at level 1 with it. reason is the passive bonus damage increase is highest at level 1 and the attackspeed also doesnt scale that well. its still very good.
e should be maxed at last and is simply an utility spell to chase opponents down and escape from ganks. ive read some guides where they recommend to start with it at level 1, imo thats foolish because it has a pretty long cooldown and when for example an ezreal walks out of it, and begins trading with you, youre kinda on the losing side.

or, if youre having a good start and succeed in getting 1650+ gold at the first buy, you can skip the dorans and should always prefer this build order and aim for an extremely early Bloodthirster at the 10-12 minute mark:

In like 70% of my Miss Fortune games this is the case and i have my Bloodthirster on the second buy and henceforth completely stomping the opponents.

Please note that thats the usual build order preference which should be adapted in certain scenarios.
For example, if you realize opponents are already stacking tons of armor after you finished your Bloodthirster and Phantom Dancer, you should consider getting Last Whisper before the GA and buy Infinity Edge at the very end instead.
If the opponent team has champions like Skarner or Malzahar who can shut u down completely with their ult, buy a Quicksilver Sash instead of the GA! Since Miss Fortune has no natural escape but tons of damage in her kit, you should always get 1 defensive item sooner or later on her.
If youre doing really well throughout the game i would even consider getting GA straightaway after the Phantom Dancer, because if the opponents arent stupid they will focus on trying to kill you for sure.

- Nunu

Pro: Makes u deal even a few more tons of damage, insane chasing and killing potential

Cons: No proper health sustain on lane, at least until you have your early Bloodthirster.
Kinda weak to ganks.

- Janna

Pros: Pretty safe to lane with her, especcially after she hits 6 she can get you out of situations where youre dead 100% otherwise.

Cons: Not as much killing potential on lane compared to other supports.

- Sona

Pros: DAT POKE LOL, with her u can push opponents so easy out of the lane, especcially if they dont have sustain. Also has alot of killing Potential since lots of people underestimate the combined burst of Sona and MF, even more so if you offensively flash in for a kill.
Has sustain.

Cons: She tends to sometimes get caught while trying to poke, especcially against Blitzcrank/Leona.

-Soraka

Pros: u can play soooo aggressive with her, since you have infinity mana and an awesome heal spell every few seconds. DO NOT play passive with soraka, u really need to outfarm your opponent hard and poke the **** out of them. Just needs proper ward coverage and be safe.

Cons: Not as much killing potential as with other supports.

-Taric

Pros: Armor Buff OP, Stun, armor shred, some minor sustain. He does really well with MF and is one of the best.

Cons: I think he has none except it might be a bit boring for the support to play him... ;-)

-Leona:

Pros: Highest killing potential of all supports, awesome cc. even good later on in teamfights.

Cons: Kinda vulnerable getting ganked the moment she engages. Shes like the best when youre ahead, but like the worst when youre behind. Also she has no sustain for you. Also oracles are kinda wasted on her since she suicides alot, but wins teamfights nevertheless.

* work in progress

** u can keep grammar and vocabulary mistakes, not natively english :P