Hi, 

You do not want to fill the bottom with gravel, as that can cause what is referred to as a "perched water table," meaning the water will remain in the soil instead of draining out through the gravel, and could keep the soil too wet for the plants. 

What type of plants are you interested in planting? Flowering plants or edible plants? In either case, you will want the containers to have ample drainage, or they will become a bathtub as you water or when it rains, and if there's more water than the plants need at that time. You can read about some container suggestions for edible plants on our container gardening webpage. It will be relatively the same for flowering ornamental plants, but you may want to adjust the potting mix used. 

You can raise containers off the patio with bricks to help aid in the drainage. Just keep in mind you may get some water staining as they drain. Larger self-watering containers may be an option to help avoid this. 

Emily