Just like champions such as Nautilus, Gragas, Sion, and Malphite, Galio's rework has made him a fit for the AP tank meta, where you can go full tank. Like his top lane AP tank counterparts, Galio's full build MIGHT have 1 AP item, or may just be full tank. There are options for that AP itme, such as Rod of Ages or Banshee's Veil. BUT before we get to that point, lets look at the build path.

What is the meta items to help an ap top laner?

• A Strong start will be 3X Doran's Ring, OR 2X Doran's Ring and Corrupting Potion after your first couple backs and,
• for defense you will get Null-Magic Mantle or Cloth Armor along with Boots and probably upgraded to Ninja Tabi's or Mercury's Treads along with a Ruby Crystal
• I've been really liking the Fellowship build (3X Doran's Ring) on Galio. I am having more success with it than with a Corrupting Potion, even against bad matchups ( Darius). Especially since Patch 7.7 where the base damage of Winds of War was nerfed but its AP ratio was increased.
  

These items will keep you relevant in laning phase and let you use the AP Power Galio provides, while still saving gold to invest into your tanky items you will need.

Why No Mercury's Treads?

Galio loves to STILL stack MR! So why no Mercury's Treads?
Let me answer this in 3 Parts:

1. You should build Mercury's Treads sometimes. There will be many times this will be a good choice
2. You are already stacking MR in other ways, more so than many other tanks. You need the additional AR somewhere. It also helps vs most Top Laners, even if they are AP (except for maybe mages like Swain). Ninja Tabi's reduced dmg you take from auto attacks, combined other shields ( Courage of the Colossus , Shield of Durand, Locket of the Iron Solari) mean it is a good buy. Mentioning Shield of Durand...
3. YOU ARE IMMUNE TO CC while casting Shield of Durand. Don't need to reduce CC time with Mercury's Treads when you can't be CC'd.

1. Going to be adding laning phase and the power of the Galio push. Punish those top laners without Teleport!
2. Teamfighting with different comps (the offensive vs defensive Hero's Entrance)