My easiest, made ahead breakfast is to mix 10% fat plain Greek style yoghurt with milled seeds and some frozen berries in a bowl on a Sunday night, then eat a fifth of it every day for a week. It gets thicker and thicker as the week goes on. Keep it in the fridge.
Quantities can be to suit you, but I'd start with a 500g tub of yoghurt, 5 tablespoon s of seeds and 5 tablespoons of berries to make 5 portions.
All ingredients available and cheap in lidl or aldi.
It can also do as a dessert. Some people use chia seeds but I prefer milled linseed mixes.