Shopify is used by a ton of smaller to medium sized apparel companies. Gives you just about everything you need. A ton of themes to work with, credit card processing, inventory management, etc. Its also rather cheap and scale-able if you grow. They have a free trial too if you want to play around.
Here's their themes:
https://themes.shopify.com/ You can always create your own too but there is probably something that works for your site.
Otherwise you can look at some other platforms.
Ecommerce Software & Shopping Cart Platform | BigCommerce
Cloud Ecommerce Software Platform | LemonStand
I think Shopify is the best because its simple and there are tons of tutorials online to help people. I've done development work for and through a lot of these companies. Used to do work on Magento and BigCommerce a lot.
Don't have any clue on the trademark stuff though.