That depends entirley on your area and its growing season. Look up what zone you are in then study everything you can.
If you are just now gardening, theres going to be a learning curve, a steep one.
Some things you can get going right away are herbs. They are incredibly easy once established and usefull for a number of things. Look for ones that are perrenials and stock heirloom seeds for annuals. Rosemary, Oregano, Parsley, Chives, etc are all examples of perrenials that should stick around pretty much all year unless you get real hard freezes, but they'll come back if you take care.
Look for plants that are designed to be hardy for your zone. If you are in a hot zone like me where we dont ever get a real "freeze", you will want high heat resistant plants for crops through the year. If you are in a cold area, that wont be a problem, but you'll want plants that can over winter well. You need to plan these things so you can have similar crops through the year instead of certain types at certain times. There are heat resistant strains of Spinach and Kale that grow well here in south florida. These are crops we usualy can only grow in our short winter. Its nice to have leafy greens all year, isntead of just November-March
Look into hydro and aquaponics if you are really serious. You'll get multiple times the volume of food in less space.
You can even grow indoors or in a temp controlled green house with hydro quite well through the winter.
There are other tricks you can use, like growing smaller variety potatoes in buckets or containers, wheather a pot or a 55 gallon drum. This will save space and give you a significant amount of food for that space. Those right there will be a boon to any depression-grower, whether for eating or trade. Heck, I've grown garlic bulbs in those skinny rectangular plastic flower pots and they came out perfect. I was also able to move them around for optimum sun, since I am horribly short on workable land. THese are all things specific to YOUR situation though.
Only problem is you gotta start now and you gotta get serious, cause if you are doing this for a depression/job-loss/self-sufficiency reason (and good on ya for doing so) the time to learn is not when you've got a packet of seeds in your hand a hungry belly.