Start with the grow lights you need now, add more as you need them. Each Stack-n-Grow Light unit has two 3′ long, full-spectrum T5 fluorescent bulbs that are spaced for optimum light coverage. High-tech reflectors direct light down onto plants for healthier growth and less glare. Start with the Stack-n-Grow Light System, and then place Add-On units on top to multiply your growing space. Add-On units include wall brackets for additional stability.
Stack-n-Grow Light System: https://www.gardeners.com/buy/stack-n-grow-light-system/8590139.html