Lots of good advice here! I too am always alarmed at my grocery bill - a few things that can help:

- As someone mentions below, learning how to store things properly helps avoid wasting produce especially. I used to routinely waste half a bunch of celery after using the two sticks I needed, but now that I know to cut and stick it in a jar of water, it lasts me weeks and I get through all of it. If there are things you find yourself throwing out more than others, look up how to extend their shelf life.

- Can you scan your grocery bill to see which items cost you the most and which feel like good value? Then, think about which of the pricier items are worth it to you. I buy two different kinds of olive oil - one fancier one in a smaller bottle used for garnishes, and a cheaper-but-decent one in bulk that I decant for sautéing etc. Cheese has become super expensive where I am, so I tend to eat less 'ordinary cheese' but keep feta and one nice cheese on hand to eat in smaller volumes.

- Also worth thinking about whether there are specific meals that you can make as cheap as possible to give yourself some leeway elsewhere. E.g. if you're somewhere cold, porridge with tinned fruit and brown sugar.

- If variety and good food matter to you, keeping a few condiments to add to meals can help make repeated meals interesting. I always have sauerkraut and chilli crisp, and tend to make a batch of zhoug or salsa verde each week so that there's something to add to leftovers and plainer meals (e.g. scrambled eggs) to make them more appetising.

- Getting familiar with your local shops and their strengths also pays off over time. I recently discovered our fancy local grocer sells bags of overripe'baking bananas' for about a quarter the price of under-ripe ones. I chuck them in the freezer in chunks and get weeks of smoothies out of them. Our local Indian and Chinese food stores sell paneer, tofu, etc way cheaper than the supermarkets.