I am looking for a way (plugin or code) to set for specific woocommerce products the minimum quantity to add to cart and the quantity increasing step. For example for product A the minimum quantity is 50 pcs. So when the user increases the quantity it should get these steps: 0-50-100-150.... If 0 is selected then it should display a message regarding the minimum quantity. Each product can have a different minimum quantity.
I think YITH Woocommerce Minimum Maximum Quantity plugin is the best solution for your purpose. It enables you to set a minimum or maximum quantity for product selection. It also shows quantity/amount error messages to your customers. Moreover, you can use the plugin to set a different minimum quantity for each of the product. So, I think it's the best option for you.