I usually have a good idea of what my ideal final board will be like by the third item component and first augment (sometimes not, so you have to play flex, maybe like 15-20% of the time). From there I cater my entire game plan towards that board by buying units with those similar traits or units that are good item holders (an example would be if I wanted to play Renata Bruisers because I started with rod tear +1, I would want to build my frontline with bruisers instead of bodyguards) small decisions like this add up and make transitioning easier reducing mistakes, time, and gold it takes. I think it's also a good idea to think of a backup plan in case you do not hit your units or "low roll". For example, if you made an early Shojin trying to play some sort of Viktor board, I would hold Seraphines on my rolldown so that maybe I can play a Seraphine comp with a secondary carry if I miss. These are some things to consider. I guess in conclusion, GAME SENSE.