See you are newer here. 1st, Greenfield's are basically easy. Many, many threads on here about it. Soil test. Follow recommendation. Make sure of plenty of sun for most all day. Plant seeds at recommended depths. Depend on rain.
Do all that then about anything works. I like wheat, rape, and crimson clover. It works for me. There are also oats, rye, triticale, radishes, turnips, all kinds of clovers, and the list just goes on. I believe if I get the first part right I can have success with about any winter hardy plant. It ain't rocket science. Don't over think it.