Gardening doesn't just mean vegetables. Fruits and berries are also great fresh resources for your three-month supply. Almost every climate in the world can support some kind of fruit. Don't have a yard? In many climates you can place potted fruit trees and berry bushes on a porch. You can even grow citrus trees or a pineapple plant indoors!
We currently have a peach tree and an apple tree (with four different apple varieties growing on it). Fruit trees can get huge if you let them, but correct pruning techniques will keep them as small garden trees. I have strawberry and raspberry plants right in my garden. Both, like the fruit trees, require maintenance and pruning to keep them from overtaking the area. Strawberries can make beautiful under-the-tree plants, which will also help contain them. (I have to place a net, weighted down with rocks, over my strawberries each year or the birds get them first.) Fruit trees and berries also work well as ground covers, or bedding plants. We also eventually plan on planting grapes.
Fruits and berries can be bottled, made into jam or syrup, dried, frozen or juiced. Because fruits have a higher acidic content, the shelf life is even better than vegetables. Our combined trees and berries produce fruit from around May until late October or November. Apples store well for several months in a cool area. So, we have fresh fruit for almost seven months of the year (and we're in a fairly cold winter area). If you live in a warm area, you can grow citrus, bananas, pineapple, figs, etc, as well as apples, peaches, and berries all year round. Besides the ongoing pruning, there is not much maintenance - besides picking and there are no seeds to store. And best of all, the trees and bushes are so inexpensive. I think we paid $20 for our peach tree. Our apple tree was $15 at Costco. The raspberries were free (starts from neighbor's gardens).
I think of fruit as a bonus when it comes to our three-month supply. There are so many yummy recipes and ways to use fruit in the meals that I already have planned. It's worth it to find a way to add fruits and berries to your gardens.