What Hans said "it´s a marathon, not a sprint" is a good thing to keep in mind so you don't get discouraged.
It took me 17 months for my first sale.
Looking at how long it took people to make a sale doesn't really tell you much since the circumstances are all different. Some have come here and uploaded hundreds if not thousands of images, some have come here with a big following, some are very good at marketing and advertising, etc.
If I were to start over I would say the first thing to do is enjoy the ride.
You are a photographer so get out there and photograph. Upload your very best, make sure you check them at 100% for quality and take the time to do good descriptions and key wording, don't spam or copy from wiki. Set up your SM accounts and use them well. Get some business cards made and actually hand them out. Start shooting collections of things so you can set up collections. Search the discussions for information on how to do all these things, the amount of information here is astounding.
Most importantly have fun with what you do.