A raised bed garden, with two foot deep beds, well planned, with proper sun exposure, with soil from the ground that is amended heavily the first fall year with peat moss, perlite, vermiculite, clean sand, and as many bags of WELL SHREDDED leaves (preferably hardwoods) that you can collect; everything dug in the winter before first harvest.
At least a foot of shredded leaves, covering at least 2 overlapping layers of heavy brown cardboard, that itself covers at least a foot of well-shredded compostable vegetable waste that is WEED FREE. No citrus rinds. Cover the shredded leaves with something like Remay row cover to keep them from blowing away during the winter.
In the first spring, dig it all in from the sides of the beds. I like beds that are NO MORE than 3 feet wide, now that I am 66 and with osteoarthritis. Make it simple, I'm OLD!!!!!!
When it gets warmer, a crop, or two, of buckwheat sown, grown to the first flowering stage, sickled, allowed to sit for a couple of weeks, dug in, and re-planted for a double green manure to get the biological juices of the bed's soil really flowing. No harvestable crops to feed oneself that first summer.
In the 2nd fall repeat the layering process with the compostable vegetable waste, the brown cardboard, and the hardwood leaves. Anything but black walnut leaves, which are toxic.
By the 2nd spring the two foot deep beds should be full to the top with highly active, friable, soil that should be able to grow almost any of the row crops that feed man.
For specific crops in certain beds that are destined for any of the heavy feeders, make allowances the prior fall with your green manures. Treat the beds the way a farmer treats, or should treat, his/her fields, with crop rotations, but MOST IMPORTANTLY, allowing at least 1 year in every 5 years for the bed to lie fallow with only green manures tilled/dug back into the bed.
UNLESS, you are trying to grow all of your own food, a small square footage, intensively planted, lightly mulched with finely shredded dry leaves to keep weeds at bay, is capable of growing an absolutely STUNNING amount of food.
Been there, done that with a 9' 3" wide × 27' long × 23" deep raised bed that was sub-divided with cross-bracing (to prevent bowing). With a set of three 2×4's screwed down across the ends, and the braces to create a 1 foot wide walkway down the center of the short side.
This had me ending up with in essence, 14 of Mel Bartholomew's 4' × 4' Square Foot Beds. In reality, the roots of the plants had seven 9' × 4' beds to grow in. In 224 sq. ft. I was able to grow more green beans, eggplant, carrots, lettuce, radishes, etc. then I had ever before. Yields off of plants were 4-5 times what the pot labels, or seed packages were calling for.
I purchased an All American pressure canner just to cope with the green beans.
As long as one keeps adding the leaves, practices crop rotations, mulches, and makes compost, a small space garden will be productive beyond your dreams.
Getting it set up is the hard part. That, and practicing patience before planting the first food crops.