As others have said a good plot depends on a lot of different things.
Climate, soil type, tillage, planting technique, annual vs perennial, etc. So there really isn't a one size fits all answer to your question. A good source of info for your area is your County extension agent. He will be able to help with general questions. Another good source of info is your local feed/seed store. They are in touch with what other plotters in your area are using/buying. I have tried some brand names like Tecomati and Biologic over the years and had good luck with them. But I have not found them to be more effective than a bag of big rack mix sold by my local feed store at about half the price.
Good Luck