I purchased several plants (herbs like cilantro and basil, three kinds of peppers, lettuce, and tomatillo) and Miracle Grow soil to make container gardens for my apartment porch. All I have left now are the peppers and a fledgling tomatillo plant. Why haven't I gotten any vegetables/fruit from them? The plants look healthy, and the tomatillo even flowered, but nothing more. It's discouraging that I can't grow vegetables.
Lettuce is a cool season crop and finished when the weather turned warm. If your herbs did not flourish you may find the Ask an Expert response at https://ask.extension.org/expert/questions/62740 helpful.
There are several factors that may be responsible for the disappointing performance of your peppers and tomatillo. Five common factors to keep in mind are space, amount of sunlight, moisture, soil fertility and pollination. Peppers and tomatillos require at least 18 inches of space around them to grow well and flower. Five gallon containers would be ideal. They also require a minimum of 8 hours of sunlight daily. Container-grown plants also require more frequent watering to make certain that they do not dry out. Peppers are heavy feeders an can benefit from additional fertilizer during the growing season by following the package directions. If space, sunlight, moisture, and soil fertility are not at issue then lack of pollination is a likely culprit.
Peppers are usually self-pollinating. However, if they are not located where the breeze can move the pollen among their flowers or if the pollen is too heavy to move readily among the flowers due to high humidity, then they will be dependent of bees for pollination services. Tomatillos are pollinated by bees and require cross-pollination. This means that another tomatillo plant must be nearby, You have only one plant, hence no fruit. Bees are opportunistic and go to those locations where the most nectar is available. Therefore, small container vegetable gardens benefit from close proximity to an abundance of flowering plants. Placing containers of perennial or annual flowering plants among your containers of vegetable/fruit plants will enhance the likelihood that bees will pollinate them.
Look for vegetable and fruit plant varieties that are suitable for container gardening. These are often small, bush varieties but not always. Seed packets and plant labels usually indicate that the variety is suitable for containers. Or ask for assistance from your garden center staff. You can also see an excellent fact sheet about container vegetable gardening from Ohio State University at http://ohioline.osu.edu/hyg-fact/1000/1647.html
I hope that you find this information helpful and sufficiently encouraging to continue container gardening. With some experimentation I am sure you will find the right mix of plants, containers and soil for your location that will provide you with an abundant harvest.