You can grow green onions from sets (bulbs). These are available from the big box stores and Walmart in the spring and they cost between $2 and $4 for 80-100 bulbs. Plant them as close together as possible and you will have green onions for your table in as few as 2-3 weeks. Pull, eat, repeat - until there are no more sets.
Below is a video that illustrates the planting. Plan the sets in a sub-irrigated planter (as close as possible). The video shows planting the sets in 4-inch pots for propagation to large bulbs. You don't need that when planting for green onions. Plant the sets as deep as possible (as deep as 2-3 inches) to get long white stems of the green onions.
The green onions grow just fine under grow lights using the previously described triple "L" concept (search the website to find it).
How to Propagate Onion Sets : Organic Gardening for Real - YouTube http://bit.ly/YC0yJl: As the nursery owner Oscar Carmona says, "Remember feed the soil, and let the plants feed you."
How to Plant Your Onion Seedlings/Transplants in the Garden - The Rusted Vegetable Garden http://bit.ly/10NcCb7