I would recommend starting with an online system such as Quickbooks. I wish I had done this from the start instead of my antiquated spreadsheet system, the business has grown at such a speed it was a bit of an oversight on my side. I would also recommend making an appointment with an account just for advice on how to get going as you will need one eventually so they can help you start as you mean to go on. I made the mistake of thinking I could do everything, you need people who can help you, so you can focus on what you love.