sure.
1. miss fortune isnt built as an autoattack champion. as such, mp boots are a better option since her ultimate does magical damage, thus making it a even better nuke. sorcerer's and berserkers give the same increase in movement speed.

2. i'm not using clarity so mana is definitely an issue. i run into a lot of mana problems, especially early game. maybe you just dont stay alive long enough to use all her mana. that's says more about you than it does about me. plus, my rune setup is exactly the same as phreak's anyways.

3. as u can see, infinity edge is the last item on my list. the game nearly always ends before i start my 5th item. at this point, your 4th and 5th item should complement what you need. if you are doing really well, get IE or black cleaver for the atk. if they are focusing you, get guardian angel. if you're having trouble with cc, get banshee's veil. i simply put IE cus my team usually does a good job protecting me.

any more questions?

seeing u put my down, from the title ill do you 1 better and explain why ur builds fails

1. magic pen boots are useless, only useful on mass AP heros such as karthus etc... u can use beserkers so much more wisely since fortune relys on speed and chasing

2.ur wasting runes on mana per 5 sec but later on she has enough mana to kill all, its useless should b used on AS or somfin since ur so called AD build.

3. why would u get inifnity if you dont max crit strike or damage in ur mastery tree??? plz explain ur smart logic