Honestly - what do you spend on food each week? And where? Going food shopping tomorrow and going to see if I can be frugal! Don't have high hopes to be honest. Got slow cooker, so will try and do maybe two meals in that this week, only issue being that I have a very fussy 4yr old :\
Depends on what frugal means to you, really. Just me and a 6yo - if i don't need lots of household bits (cleaning/washing/cat food etc) can do it for £30-35 and that can even be from Waitrose. If we have a week where I am money watching, we eat jacket potatoes, eggs, baked beans, pasta etc. I make good use of the freezer, so always have a meal or two from that each week. Essentially - only buy what you absolutely need, do not buy anything because you fancy it and do not buy alcohol. If you need fruit, markets are cheaper.
We spend c£35 at Aldi for 2 adults plus a top-up shop at Tesco or such like for bits we can't get at Aldi about once every couple of months which is normally c£80 but includes a lot of vege stuff (incl. branded e.g. Quorn).
If you are trying to save money then soup is your friend! A big pan of vegetable-based soup (4-6 portions) should cost about £2-3 and can be used for one or two dinners a week plus lunches at work or as a starter for your Sunday roast so you don't need as much meat, etc.
Soup is also good if not your not a v confident cook as its quite hard to get soup wrong! Minimal effort too, I always do blended soups because then you don't have to chop the veg neatly and my hand blender was less than a fiver from Wilkos. It will use up veg that is going soft to save chucking and can be bulked out with lentils (red are best for blended).
Can you tell I like soup
My other tip would be never throw any leftovers - even if its half a portion pop it in a tuppeware and bung in the freezer. A small portion of chilli/bolognaise, etc can make a topping for a Jacket Potato or pasta can be a lunch at work.