Step 1: purchase domain name. I used Namecheap to buy onefuckingshirt.com as it holds a few other domains of mine.
Step 2: Purchase hosting, I was being lazy so I immediately decided this was a good time to test out Shopify.com, for those that don't know, you can open a store on their site or use their hosting services to build a store that is shown both on your own domain name and their domain name. It isn't free, I opted for the $14.99/mo plan with a 14-day free trial that is rapidly disappearing. From what I can tell, all they really provide is payment processing for you and easy wordpress installs.
See current site: www.onefuckingshirt.com
Step 3: Register for printful.com and integrate into shopify.com - this is in the APPs section of shopify admin page. Printful is essentially a printing and shipping service all in one, allowing me to submit my shirt designs and have them print and ship on an as-ordered basis. This eliminates any real overhead and a little profit margin, but will help me save time when I'm busy being a full time engineer.
Step 4: Order samples of shirts. They will arrive soon! Printful is nice enough to offer a decent discount on samples.
Step 5: Evaluation of shirt sample. Things never work the first time, if they do, you lucky fucker.
Step 6: Social Networking. Do it, in fact this should be Step 0, it should be part of the core of your business. You don't just make money by making a website, sitting back and waiting for money. Time to learn to be a copy writer.
The failed shirt does not look so bad for a first shot! Have you considered sending a test pattern (i.e. a wide range color palette with different shades and saturations) to your t-shirt printing service, have them printing the test pattern on a the relevant types of shirts, get them back, scan or photograph them and calculate a correction map to prewarp your t-shirt designs? That way, you'd establish sort of a end-to-end color consistency with a chance of getting even photorealistic prints just right on the first try.