I feel like I'm in a similar position because I'm a student and don't have a lot of disposable income.
I usually buy a big bag of frozen peas, sweetcorn and carrots for around £1 each about once a week. Also buy 1kg of pasta or rice, whatever you fancy which is also around £1-2. Then I buy chicken (usually diced) which is £7 for 700g which lasts me four meals. The chicken can definitely be done a lot cheaper though.
My diet is pretty rubbish and a constant work in progress. I often skip breakfast and have a lot of shakes with oats in but recently I've started buying baked beans and eggs to have for breakfast too which I imagine will get my calories between 2000 and 3000 with two meals like above. I'm not sure how much they cost when bought in bulk because I haven't got round to it yet but I'm sure if you go to a farmers market or something eggs are really really cheap.
Another thing I have as an option for some more carbs is cheerios (cereal). They're a pretty nice snack and can easily be another 500 calories or something like porridge. A litre of semi skimmed milk is about 500 calories too and costs me £1.
All in all I'd say I could easily eat at least 3000+ calories each day, without any supplements, spending about £50 (80 Australian dollars) a week and that's with my bad shopping habits. I'm sure I could cut it down £10 or £20 if I tried. If I can do it you definitely can because I'm very lazy and I hate cooking. Like I said I'm working on it still myself but I hope this helps.
Oh and also a lot of the stuff I get like meat and milk I can't buy in bulk because I have extremely limited fridge and freezer space.
Look up big on a budget by animal on YouTube, there's some really helpful videos.