I love growing gladiolas in container gardens. I tend to pack the bulbs pretty tightly in the pot and use good well drained soil. Gladiolas like full sun and take awhile to bloom. I usually cut the stalks when the first few blossoms have opened to bring them inside for cut flowers. They last well in a vase and I'm fascinated by watching the blossoms open one after the other.
You can buy bulbs in your local nursery or from a mail order specialty house. These beauties came from Brent and Becky's Bulbs.