Start with boots and 3 pots very useful dodging and healing early game. Then get a avarice blade for early gold then move on to phage for damage,slow and health. After phage probably want to finish boots the best boots for her mercury or ninja again depends on what your against if you get ninja's I would later get zephyr because tenacity is grate for her. Then you probably want to get another defense item like warden's mail or hexdrinker it depends on what your against. After all that you really need to rush for trinity force because that bonus burst damage really helps. What goes grate with trinity force burst damage is more damage like maw of malmortius, black cleaver or youmuu's ghostblade(for more attack speed). Those items give a little defense all your items you want to be a little tanky so you dont get squashed in team fights. If your getting targeted in team fights probably want randuin's omen or thornmail if there more of a attack damage team; if there ability power team you should have maw of malmortius if thats not enough then go for banshee's veil ,mercurial scimitar or wit's end. Last of all if you have covered everything and slot open just get damage like bloodthirster, infinity edge, ravenous hydra, last wisper or whatever you want good.

good luck have fun