FYI - Onions are real easy to grow and can be started by either sets or seeds. I always start mine from seed. The only thing you have to pay attention to is your growing location because onions have both short day and long day varieties. The difference is the amount of daylight required for the onion to form the bulb....snip...
so I bought a bag of yellow onions and a bag of sweet onions.
I grow short day onions due to living in georgia. 100+ yellow onions like you find in the grocery store don't really take up that much room. I grow grando 1015 and normally start my seeds in waves starting around dec 1'st and plant in the ground once the seedlings are around 2 months old if the soil can be worked then.
I also grow a couple of multiplier type onions, egyption walking, potato and a red shallot. These varieties honestly are not as easy to eat as the grando 1015's due to their smaller size but actually have a stronger onion taste. Advantage is that in a SHTF I'll always have onions to eat. My egyption walking onions stay in the ground all year where as the potato and shallots get harvestly like normal onions and then replanted in the late fall.
Garlic is another easy thing to grow at home which also does not take up much space. I'd recommend hitting up a farmers market to buy a type grown locally in your AO but even the bulk ones from the grocery will grow decent. Garlic comes in both softneck and hardneck with the softnecks being grown mostly in the south. But in my AO of n.ga both types can be grown but with the softnecks usually doing the best.