A neat, well-planned garden maximizes a small space. For example, when you plant multiple rows of lettuce, leave several inches between them. When your area is clear from frost, plant a row of bush bean seeds in this vacant area. As the lettuce is harvested or comes out due to heat, the beans will happily take over the area.
Cluster like plants together. One or two pepper plants can occupy a corner, while several eggplants might linger in the middle, and a small squash selection such as 'Prolific Straightneck' will eagerly consume one side. For climbers add a bamboo tepee; snap peas and tomatoes go vertical and take up little surface space.