I believe quite a few retailers have now created Google Product Listing Ads. If you have not take a look at this post which guides you how to create Google Product Listing Ads -> http://wp.me/p1whJ0-ok

If I am a retailer selling products across the range and would like know which category is performing well, I can find it out through Google Analytics. I have lined up some screenshots how to do so.

Please do let me know if have any issues doing so in comments section.

Click to View Screenshots