Like the others have said, put more of your thoughts down here and we can see what we can suggest.
You don't need a huge garden or allotment to be more self sufficient. None of us will ever attain total self sufficiency, but we can do our best.
Things like solar power, wind turbines cost money and are long term investments, but starting small, things like not wasting what we do have, whether it be saving washing up water to water certain things or help flush the toilet.
Not wasting left over food. On the odd occasion when I cook too much, what I don't use gets frozen in margarine tubs or little plastic bags and used for soups, stews, curries etc.
I make nearly all my own stuff, to us fast food is an egg!
I make my own wine, butter when I can find the cream cheap enough, bread using the supermarket own brand strong bread flour, jam, usually using my own apples and blackcurrants.
Recycling things we might otherwise throw away. My OH makes logs from shredded junk mail when he's in the mood, I save any bits of wood I can find for the woodburner and occasionally cook on the woodburner too, plus I have a kettle suitable for woodburners.
Saving your own seeds when you can from things like tomatoes, peppers, runner beans once you get your little garden up and running.
Although you only have a small garden, think growing up as well as across. As well as my runner beans, I save some of my alderman peas to re-sow next year. Small fruit trees, either the skinny minarettes or up a wall as an espalier.
All helps save space.
This is only the tip of the iceberg, wait until the others come on here with more ideas!