As Jeannie mentioned, Rio Grande is a good source for materials. You should be able to find pre-alloyed materials i.e. 14K rose gold ready to use in a variety of forms. If you wish to alloy your own gold, Rio has a calculator on their website for that too. The amount of gold needed will depend on a variety of factors including the method of production (casting vs fabrication).
Otherwise, I believe @dataguy has a class on the calendar that might help get you started. If you can’t wait for that or if it’s full, PM me and I can help you.