There are many websites where you can sell your app!

The best place is on www.fiverr.com, auction type of selling!

www.codester.com/start-selling‎
Make Money By Selling Your App Code Work

www.chupamobile.com/sell-apps
You can become an author and start selling your iOS and Android Templates to a huge group of interested people. You can build a Business by Licensing your App Templates, Game Source Code and Components.

About marketing and increasing downloads in app stores send me the link to the app so I check it out.
I do great ASO!