Fry lite cooking spray is a must.
Sweetener instead of sugar for hot drinks
Swap full fat milk for semi or skimmed.
Swap butter for extra light flora or use extra light laughing cow cheese triangles as a butter replacement.
Mugshots are great if you like pasta, a lot of them are syn free.
Then it would be a case of what YOU like to eat. Are you following the green, red or EE?
Stock up on vegetables, fresh or frozen. Eggs are free, as are oxo stock cubes. Stuff like Pasta n Sauce are great as they're low syn or free and handy when you can't be bothered cooking from scratch.
You're going to want to be planning breakfast, lunch and dinner with things to snack on too so work around the meals you want when planning what to buy. I sit with my SW books and nose through for low syn stuff.
At the mo I'm doing cereal for breakfast, sandwich or something on toast for lunch (beans or scrambled egg) and then veg and quorn for dinner or home made soups/stews. Mugshots, quorn slices and yoghurts for snacks.