Building a Battle Ready yeti

is awesome!! but I am having trouble with my build.

I've gotten to the point that I can start Strong Most games but in the second phase of the game maybe around lvl 8 or 9 when I am looking for a second trip to base things fall apart.

I start with and usually can get the First Dragon, a few assists, almost always help push for the first turret and maybe a kill or 2. After this point if I build full tank I can rack up a bunch of assist but I can't 1 vs 1 at all (but I can usually run away) and getting kills is almost impossible unless I blatantly start Kill stealing.

I've tried adding Ap and Atk Speed but when I do I turn into a feeder when I try to gank or join team fights, Can anyone help me find the right balance of Items