I think that this build is focused and accurate to how she should be played. With your 2 nukes its smart to get Hex Gunblade and Guinsoo's Rageblade then stack ATK spd for extra healing and more effect out of your rageblade. Other good on hit items like Bloodrazor and Frozen Mallet work well for her, imo. Trinity force is a good fit for her as well. Very nice build +1!

EDIT: Some thoughts on her skills. I would focus building her W ability first however. She shines more as a late-game champion. Early on I believe that the life on hit and added true damage on activation make her more resilient and easier to lane effectively with. Getting 1 point of each nuke early then maxing W seems like a better route. Then maxing her Q next, its range is what makes it her superior (albeit still weaker in overall damage) nuke. Her E is more for the CC and can be maxed last since the slow/stun effect is more for ganking and late-game killing. Early on its only good for small team fights or for escaping ganks. My 2 cents.