I like starting either boots or brawler gloves, then building the glove into avarice, and getting t2 boots. Usually defensive ones. If im doing fine and dont need the extra hp I work on brutalizer, then phage (switch those around depending on how you are doing) and get Frozen Mallet from there and the rest is just counterpicking. Items I like for him are Maw and Atmas (defense and crit chance for his E). I use my E as my main dmg source. If you are facing someone like rengar, ignite really helps because you can ult ignite him so that he doesnt have a chance to stealth away (this works for champs like shaco as well, but the silence should be enough for shaco since they are generally squishy.)
So boots, yomumus, IE, FM, Atmas, Maw is my favorite end game build. Always look at your death recap though. Plan accordingly.