Too late now but... if you are planning to change how you eat for good ie not just a temporary diet, you need to plan and prepare in advance.
So read about different ways of eating, decide what your “rules” are going to be (low carb etc), draw up a meal plan that fits within those rules, then create a shopping list that fits your meal plan.
At the same time, before you even think about shopping, clear your cupboards / fridge / freezer of everything that doesn’t fit yr guidelines. think about how you are going to handle family members eating food that you will not be: will you be able to have them in the house? Think about how you will handle changes in your schedule, or what to eat if your in a rush. If you are an evening snacker, and that’s not in your plan, think about what you will do to avoid this - starting a new hobby, going to bed early, whatever. Do you have time to cook from scratch? If not, you’ll need to plan how to create that time. Good food often costs more - are you prepared to spend a bit more on food shopping, and are you able to shop more often if you are planning to eat lots of veg and salad?
The planning and prep part of changing how you eat takes time and effort. But it’s the only way to make thing stick. It really makes you focus on the potential tripwires - you might love the food you eat but if it’s too expensive, too time consuming to prepare, doesn’t satisfy your evening boredom snacking, etc it’s not going t stuck for the long term.
Eating is habit: you want to change your habits, the things you do every day. The food you buy is only a small part of that, and tbh it’s pretty straightforward what the main ingredients of a healthy diet are: as pp says lean protein, lots of vegetables and salad, some fruit, some fat and dairy and nothing processed / sugar / cheap carbs.
But if your life is structured around eating ready meals, takeaways, sandwiches, evening snacks, having to fit in with family members, etc - it’s the habits that have to change as much as the actual food you buy.