It happens over and over many times that i buy the same skins twice , that i already own. Sure its not the average player problem because many people know their 20 to 50 skins they own, but i have many hundreds and there is NO easy way to check if you already own the skin while you are browsing the shop and check for cheap skin offers.
Its always, logout of the store and search for the skin in the character skin browser IF you own it, and then login to the store again. When you have over 500Skins, you can imagine what a shitshow that can become for every new skin you want to buy.
The Shop could need some love, from the “scrolling” options that are non existent with middle mousebutton autoscroll or the missing option to see if you already own that skin before you buy.