>>52883091Eat food when you need a specific effect like encounter power to find a rare spawn easier, raid power to get bonus rewards from raids, etc.
Custom sandwiches are the best since you can make basically any type and ability combo you want. The premade recipe book is good for main game and searching for a specific ability if you don't know how the sandwich system works.
Buy ingredients like whenever, I would buy like 10 of everything you don't have yet when you see it.
Eventually if you want to go for shinies, these recipes attached are convenient. There's a dozen different resources scattered around online for other more specific recipes, so just Google search for a specific ability + type if you're curious or try to theory craft a sandwich at this link
https://cecilbowen.github.io/pokemon-sandwich-simulator/ 
