Before you launch into gates and large arch type things, try to design and forge a bunch of garden stakes. You can try out a lot of designs and work out construction details without a large investment of large cross sections and heavy forging. Stakes around 3 to 3 1/2 feet tall sell fast at garden events, Price them around $25 0r$35 each. You should be able to sell a couple dozen before lunch. If you take a walk through size gate to a craft show type thing you should charge $2500- $3200 for it and you will probably take it back home with you. I have made around 55 gates (a couple were over 15 feet wide) and thousands of forgings. People like to buy things that they can take home in their backseat.