I'd say avoid the term "self sufficient" because thats a lot of work and a low standard of living; I suggest you want to discuss "lowered dependence" and "buffered from supply shocks."

In the suburbs and cities you may not be legally allowed to do things like drill a well, or have your own sewage treatment, nor things like gardening or raising livestock. If you're lucky in that respect or willing to flout the law you still have the neighbors to deal with, not just "will they turn me in" but how different can you be before they turn on you? especially when they're feeling social stressors that you aren't?

If you want to do this for real, get rural.

On the other hand, small gardening and having as much nature as you can in a city is viable and fine and lovely; its just not going to be a winner in terms of feeding you or isolating you from the corner vegetable stand's supply issues. Nothing wrong with container grown salads and pride in them; but you're not shifting much of your food bill tot hat and the time investment will make the economics suck. You have to add in the personal joy of tending the garden to make it pay.

Rural life is the same but with much more "how does this make sense?" that can't be answered without intangibles on the accounting sheet.