
I would add to these suggestions the humble parsley. Parsley is loaded with nutrients, and is cheap. What's more, you can grow it easily in a container on your porch. If you're making crockpot soups, add a handful of freshly chopped parsley right before serving.

Nutrients in plants come from nutrients in the soil, so be sure to use quality, organic potting mix or good, clean dirt with soil amendment. Start now! Spring is upon us.
Now is also the time to check out local Community Supported Agriculture co-ops. For a seasonal subscription, you get fresh produce, often at great prices compared to grocery store prices.