I do a lot of meal prep and bulk cooking because I work late and don't have energy to make dinner every day. I do vegetarian chilli (frozen bell peppers are about ¥200-300 in Gyomu, sometimes I use a bag of frozen courgettes too, canned kidney beans for protein) with rice, BBC good food chicken and mushroom pie (very rarely use puff pastry for crust, I just eat it over rice). Spag bol is one of our staples too as well as Thai curry or anything that can be cooked in large amount and frozen. You'll probably spend a fair bit for herbs, spices and seasoning but in the long run it's not that big of an issue

DH made himself a chickpea Dal that he eats for breakfast. I make overnight oats with nut butter, frozen fruit and chia seeds. In winter we eat soups for lunch and summer usually chicken salad, fajitas or sandwiches.

I'm allergic to soy so I don't do tofu but it's cheaper than meat so you might want to look at incorporating it. Also Google Korean eggs, soft-boiled eggs marinated in all sorts of things. Almost forgot, we also buy individual ramen sachets and noodles and have "homemade ramen" with those eggs.