I play jungle Diana. Why? Her clear time is absolutely crazy. one Q, and a Shield + Auto Attack will clear a camp (this takes about 1.5 seconds) With a Jungler, you are able to maintain altar control, be higher leveled than anybody else, and win the game. Summoner Spells I bring are Surge and Exhaust.
lolol Surge right? no. It gives you an insane attack speed buff, as well as ability power. Surge was made for Diana, who every three auto attacks basicly gets a free Q. It's insane.
For Masteries I run 0/21/9, taking Movement speed whenever I can.
Shadow Isles' Meta is Bruisers. People who can deal out insane damage while taking some.
Diana is perfect for this, able to leap, A REFRESHABLE SHIELD THAT DOES DAMAGE, a pull back, and a huuuge damaging AoE.
I start Boots + Cloth, 3 red pots and 2 blue. Start at the lower wolve camp and work your way around ganking whenever needed. (Bot, most likely as it's a 2v1 lane.) Maintain heavy altar control and GG.
You want to go for a tank-everything while damaging build. Merc Treads, Rod of Ages, Abyssal Septer, Then Rylais, Deathcap, and Randuins (Active wrecks them) is pretty standard for me, but feel free to throw in a Nashor's Tooth.
9x Greater Mark of Alacrity (15% Attack Speed + Her Passive OP)
9x Flat Armour Yellows.
9x Flat Magic Resist.
3x Movement Quints.
Sorry, way more then you needed, but have fun everythingstomping<3