Clover will last longer and usually cost more for the seed,wheat and foraging oats are another good thing to plant and is easier to get started these would be good to plant in the early Spring.
We usually plant Brassicas,Rape and Turnips along with some groundhog raddishes in the Fall around the middle of August or early Sept.,as mentioned get a soil sample and a PH reading to see what the soil needs to help the seeds grow better.
In the Spring time around late Feb or March I frost seed clover in the spots we mow along the field edges or logging roads,this is also an option for those that don't have a lot of equipment to break up the ground!