Welcome to Slimming World! I'm a recent returner but things don't change much. I do both green and red (and EE now) and my staples are:
Fridge/freezer - syn free yogurts including natural for sauces & marinades, ham, mushrooms, peppers, toms, mixed salad stuff, quorn mince, very lean minced beef, chicken, bacon, lemons, limes, syn free sausages, salmon filets
Veg - pots (bakers and new), lots of mixed veg in freezer, onions,
Fruit - anything and everything
Cupboard - tin toms, stir fry veg, beans, red kidney beans, pasta n sauce, rice (uncle bens, risotto, basmati), pasta, cous cous, curry spices (tikka, tandorri & medium), any other spices i.e. chilli flakes
Healthy extras - cheese, ryvita minis, milk,
Syns - low syn crisps i.e. quavers etc
I make everything from scratch I've built up quite a good range of flavourings.
I'm sure there are tons more but that lot will see me through most weeks, no problem.
Good luck, you'll love it!