Living in Eleve for a year, it's nearly impossible to just live off of restaurant food. We are all poor students, so here are some tips, where to buy your ingredients cheapest.
Close to Eleve, there are only a few supermarkets. The closes shop would be Lawson, a Conbini, which is nice at 2 in the morning but sells everything a bit more expensive. I recommend going there for your breakfest when you're late, but at any other time between 10 am and 11 pm, go a few steps more in direction to the train station to a shop called "Welcia". They are a drug store and have some food as well. Alcohol, snacks, ice cream, drinks, instant food (oyakodon, ramen etc) and cornflakes, bread, milk, cheese for breakfast. It's a good shop for those, that can't really cook, because it has food like oyakodon or curry that you just prepare a little and pour over your rice.
If you need real food, there are three places you can go to. In direction of the university, there is a supermarket called "Ookuwa" (next to Family Mart). It is a bit overpriced, so I hardly ever went there, but as I heard from a friend, they sometimes have bio products. If you think it's important, I guess you can check there. But for being a bit more expensive, they have some products that you can find only there. If you like strawberry milk, gacha-gacha machines in front of the shop or like I mentioned bio products, this is your shop.
Lastly, there are two supermarkets at the train station. It's hard to go there, but I always bought my stuff there. One is called co-op and is below Daiso. If you want to buy meat, I'd recommend you to go there. They have a lot and mostly cheap meat. If you go after ~7pm, I think they also sell it cheaper. Not only meat, but also other stuff like dorayaki or the ready made food like fried shrimps, hamburger etc.
The other supermarket is called izumiya and is in the main shopping center, where there's also Mister Donuts, peach club etc. Izumiya is big and has everything you need, but I only went there, when I was too lazy to go to co-op. The good part about izumiya is, right next to it is a vegetable and fruits shop. They sell everything cheaper than the supermarket. Fruits won't get as cheap as you might be used to, but mostly, they are cheaper than in the supermarket. Also, eggs are cheap there!
If you happen to go all the way to lalaport, I'd also recommend going to the supermarket there. By bus it takes ~230 yen on way. They also sell vegetables and fruits really cheap, and as far as I know, it's also bio stuff. I got 0,5 kg of Mikan for 220 yen there. So definitely go there!
One other secret tip, if you happen to go there, is behind Momoyama. There is a shop close to the Sakihana Hospital. It's called Seiyu and is advertising, that it always has the cheapes prices. So if a supermarket somewhere in Izumi sells cheap milk, they will also sell that milk cheaper. It's a bit far, but if you have a bike, I'd recommend you to go there. (Link in google Maps) Last time I went there, I got some lovely chicken meat for katsudon for 200 yen. And it was a lot for that price and delicious.
In general, I'd recommend you to buy your own shopping bag. If you use the card at the cashier, you can save 2 yen every time. If you sometimes forget it, it's not too bad, since you can still use the bags for your trash. You are only allowed to use white or see-through bags, so you can actually save 100 yen for trash bags, if you sometimes use them from your shopping. But always getting their trash bags will make you drown in them, so use your own bag sometimes! Not only for the 2 yen, but also for our world.
Also in every supermarket (except Seiyu maybe), it's better to go later, if you want to buy anything that's cheap. If you have certain meat in mind, it might be better to go earlier, since for example minced meat is often sold out if you go there late. Aside from that, if the meat is expiring soon, you can get up to 20 % off.
Also, izumiya and lalaport have discount cards. You might consider making them, even though I never did. I think you can also get things cheaper, if you have a certain amount of points.
Aside from that, I can only recommend you to never go shopping on an empty stomach. ;)
