Using Payment Gateway Stats
You'll need a copy of Payment Gateway Stats to proceed with this guide. You can get the plugin here.
The plugin has no settings and is ready to use after activating.
Version 3.0+
Once you have activated Payment Gateway Stats a new dashboard is added to the WooCommerce menu called Gateway stats.
To see which Payment Gateways are used the most on your web store navigate to WooCommerce > Gateway stats .
Versions older than 3.0
Once you have activated Payment Gateway Stats a new dashboard is added to WooCommerce Reports.
To see which Payment Gateways work best for your shop and how much orders and transactions they process navigate to WooCommerce > Reports > Orders, and on the sub-page click Payment Gateway Stats.
Just like other reports you can choose to see these numbers per Year, Month or the last 7 days.