To go in depth on the financials of a business you should think about Summary Learning: The Financial Model. But it's important to understand what the key metrics are you want to have in mind when evaluating a business. For some businesses the most important metric might be net dollar retention or customer acquisition cost
You'll need a lot more than the three financial statement to get the full picture of how a business is doing. Aside from dollar-based numbers, there is a TON of important metrics that are just as important.