[Nathan]

As far as I recall, soba noodles and natto were fairly cheap. I was doing a natto/rice breakfast for a while when the cash was being stretched out.

Osaka has a lot of restaurants. You'll be sorely tempted to go out a lot.

I never had much experience with the smaller grocery stores, but Donki Houte (ドンキホーテ) seemed to be a decent place to pickup non-perishables. There was another grocery chain, I think it was called Life (had a clover for a sign) that was a bit on the pricey side.

For getting around, the JR lines are decently priced.