There's really no magic metrics formula. It's better just to get started and see what you can uncover than focusing on perhaps if it's the perfect mix. I was working with a large retail chain and they had some metrics around conversion of shopping carts into orders. And as soon as you put the credit card thing into the cart flow, you reduce the conversion rate because it's extra friction for the customer. So that's something to look out for when you start trying to measure stuff is that because you get what you measure.