It would really help us assist you if we knew a little about
* Your climate
* What your ultimate goal was.
Will this be pasture? Food forest? What kind of soil, and is it hard pan, or friable already? What are your time constraints?
This all matters in making seed selections.
An overview of cover cropping, from a permies perspective, would be to mix a wide variety of suitable plants.
Legumes will help capture nitrogen from the atmosphere, and leave it in your soil for other plants to utilize.
Brassicas encourage other types of soil biology, as do all plant families.
Each plant family has its benefits to the soil.
A good mix would include both grasses and broad leaves.
If you are trying to build soil as part of your plan, you
should look at the
root structure of the plants you choose.
For example, daikon radish has a beefy tap root which can not only penetrate deeply, but leaves a massive amount of organic matter to decay in the soil. Other plants have fiberous
deep roots, while others spread only in the top few inches of soil. If you can mix all of these traits, you will be creating a very friable soil at multiple levels.
Each plant has its advantages, and disadvantages. By selecting a good mixture, you can reap the rewards of each, while at the same time, improving the balance of the soil food web. To grow healthy plants, you need a healthy soil.
An excellent book has been written on cover crops, and is a free download here:
Managing Cover Crops