First of all, sorry for my bad english

OK, let's get started, attack speed diana, you may think it's not viable, that's the same thing I thought, but i was wrong, AS diana is beast
As many people might think, AS doesn't means that she have to build AD items, in fact her items do magic damage such as wit's end, malady, etc

She needs attack speed, that's why mark runes are alacrity
Jungler=seal of resilience
Some magic resist with the glyph of shielding
And Ap Quints, ok this 15ap is quite helpful, she only needs it to early jungle runic affinity are very good on her

In the offense tree you have 2 options, you can go for attack speed or ability power, that's up to the player
12 points in the defense tree to jungle better and 9 in utility, 2% movement speed and

Wit's end its a MUST have item
Malady its a must have too +25 ap
ionic spark, it's not that important but its quite helpful if you want to clear minion waves faster or the jungle, each third attack her passive BOOM, and the forth its ionic spark passive +250 health (not bad)
since your only cc is E, you will need something else, like phage, it gives you health and that slow which is really important to gank and succeed, after phage you can build frozen mallet (at this point you will have around 3100 hp) or trinity force +AS +25ap and the slow 35% isn't that bad