I recommend to utilize walmart.com , lightinthebox.com , You can find Men and Women's athletic wear.
And,To import things and thing reviews from above locales by utilizing our dropshipping application https://apps.shopify.com/dsmatepro
My name is Jade, I am with the Social Care Team at Shopify!
You may be interested in some of the print on demand apps that are in the Shopify App Store to design athletic wear items for your customers while still having a drop shipping model for your business. Printful is one that allows you to print on leggings, t-shirts, hats, beach blankets and other items. Pillow Profits is an app that will allow you to print on shoes and make them custom.
You can try Walmart , Amazon, eBay or us.banggood. And our software can help you import products from these platform to your Shopify store. Visit:shopmaster.com