The first step of course is to choose which plates or dishes you want to use for your plate gallery wall. These could be a variety of different shapes and sizes or uniforms.
As with any decoupage project Mod Podge will probably be your go-to and depending on the finish you want you can go for their matt, gloss, or crackle versions.
The most important step and the only one that isn’t optional with this project is to make sure you are purchasing the right sized plate hanger discs for your plates.
You need to measure the flat space on the back of your plate for width and buy the biggest disc that will fit. This listing for Plate Hanger Discs has a variety of sizes for different-sized plates.