Kassey here from the Shopify Guru Team! We have some great resources that will help you with the design aspect of your store that I think will benefit your business. Be sure to check out:
I hope this helps, but if you have any further questions - be sure to reach out to Shopify support!
I'm a newbie as well. The one area I would recommend focusing on is what problem you are trying to solve for your customer. Answer the question "So what" about your merchandise. The market has become oversaturated with athleisure wear, so to stand out you need to meet your customers needs. Do you have special fabrics that solve a problem for athletes? Do you offer unique sizes? A special fit?
Hope this helps!
Being online trust is the important feature and How do we trust your website? I suggest to add Trust signals like policy pages, refer this link https://www.shopify.com/blog/6362560-shopify-now-offers-ecommerce-policy-templates
I would suggest placing a product review application on the store that will help boost buyers trust on your store
Hope that helps,