Predecessor Builds > Gideon > Gideon Midlane Variants
I like using tempest which I rarely see others use with Gideon. The extra damage dealt when using ult is pretty big, and you heal depending on how much damage was dealt, giving you options to fight/retreat after using ult instead of instantly dying.
Against Morigesh: Use Epoch instead of Tempest. Basically negates Morigesh's annoying ult.
Anti-Tank: start with megacosm instead of combustion, OR keep combustion first and use megacosm third in place of astral catalyst/dream binder
Alchemical Rod Build: you'll need to control river bugs or work in an item giving management early on. Once build is complete either upgrade alchemical rod or sell and buy something else.
If opponents aren't that great and you're not dealing with any stuns etc when using your ult, delay the truesilver bracelet until it's necessary or replace entirely with one of the substitute items.