VarkTech Pricing Deals for WooCommerce is a good plugin to create custom pricing rules.
You can see examples here: http://www.varktech.com/documentation/pricing-deals/examples/ and easily follow the suit.
I personally wanted to create a rule to limit my customer to buy only one free product per shipping. And it is totally possible with VarkTech Pricing Deals for WooCommerce.
Of course, the free version has its limitations and when one creates a rule in free version, it automatically applies to all products. But hey, you still have more to choose from.