Your website is great keep it up!
If you dont have any design experience getting a design would be a wise choice.
I went to college and majored in design and still hired designers and illustrators to make tshirt designs for me. I knew what my strengths and weaknesses were and my strengths were not in drawing.
You can check out emptees.com for designers.
I would start out with who you want to sell your clothes to. What do they want? Where are there holes in the market you can fill? Find the right market and being able to reach them is half the battle.