Hi Debbie,
Marigolds are one of the easiest flowers to grow. You can start them from seeds or transplants. Transplants will give you blossoms quicker. I buy some transplants and sprinkle marigold seeds between them. That way I can have color right away but then the seeds fill in the gaps. Keep the seeds watered while establishing. Don't let the transplants dry out either but they won't be as senitive to lack of water as seedlings.They like full sun and will perform best with lots of sun but if they have half a day of sun they will also bloom but maybe not as much.
They aren't very picky about their soil but to get the best results grow them in soil that is fertile. It is always better to improve your soil with compost than to try to grow something in poor soil and pour on the fertilizer. Roots need soil that is loose and not clay like, they need air just like we do and clay soil has little air or room to grow in. If your soil is sandy then you will need to water more often. Adding compost will also improve sandy soil.
You can collect dry seed heads to have seeds for next year. Once you buy some marigold seeds you never have to buy them again. They are super easy to collect the seeds from and store.
Bye, Diane