Once you have gained experience in selling and product knowledge, you could supervise a team of retail assistants or customer service advisers.
You could work as an assistant manager, helping to run a department or a small branch. You could work as a senior retail assistant, with more knowledge of the products that you sell. Some roles are off the shop floor, such as merchandising or buying.
Like most things, the more you put in, the more you get out...
Harrison Muyeji, supervisor/shift leader at a leading supermarket