Im selling an iPhone case that I know will be intriguing to my target market. I realize that in order to bring in sales I have to advertise. I'm targeting females aged 15-40. Where should I advertise?
You have two major challenges:
1. Driving traffic to your website.
2. Making them buy there.
A single SKU does not usually make an Internet business. What is the product? What is your current web traffic. who/where is it coming from, Is there already a want and desire for it in the market?
If you do not clearly know these answers, then you must rethink the whole process.
If you have a single product that is consumer oriented, plant seeds by testing on Amazon and/or eBay. The most female-skewed social media site is Pinterest if your product may sell via visuals.
Your question is screaming "I need a Business and Marketing Plan." You must start there.