Growing in containers is very different from growing in the ground. I've been growing peppers, tomatoes, herbs and more in containers for 20+ years. I had the best year ever last summer when I used a mix of 5 parts pine fines to 1 part peat to 1 part perlite, or 5-1-1 as it is called in the container forum. It's also important to use large containers (at least 10-15 gallons for indeterminate tomatoes and 5 gallons for peppers). Check out this very popular thread in the container forum if you want to learn more.

Here is a link that might be useful: More about 5-1-1 mix