Left to right usually, can skip some items or rush others depending on need!5 items
Rich!!!
The importance of items here go from left to right but do not just blindly follow that, build depending on your current build and what you need! Also Refresher Lightning scroll should be bought together6 items
Lane Options!!!
6 items
Optional Greens
5 items
Situational
10 items
Personally, depending if you want to or not, choosing your first T3 upgrade is dependant on game state, Pillow if you dont wanna think and wanna output more damage, Tag Along if teamfighting has started a lot earlier, and Helpers if you are playing some split push playstyle :3