Bookkeeping is your key action in getting your financial shit together. I won't lie: setting it up is a big job. To curb the overwhelm, I recommend taking it in small chunks. Try to get years of mess settled neatly in a new system in one day? You will have an emotional breakdown. Give yourself some space to learn the system, and schedule regular sessions to use it? Yes - that's how you succeed. Aim for improvement, not perfection. And remember, you're getting a year of guided group work sessions, so you will get a bunch of practice before you're flying solo.

There are two options here. 

Option 1: No Fear Taxes: Simple Spreadsheet Bookkeeping System. This is my own system I use for my painting practice, and developed over 15 years as an artist and accountant. If your goal is getting your numbers organized for a simpler tax experience, this is for you. You can use it to calculate estimated quarterly taxes, for sure, and it has built-in formulas to help you. However, because it is simple, it has some limits: if you need payroll, reports (like a Profit & Loss statement, Balance Sheet or Cash Flow statement), or if you are a product-based business that tracks Cost of Goods Sold and does not file a Schedule C as an "Independent Artist Writer or Performer" (NAICS code: 711510), then you will need bookkeeping software, not my spreadsheet setup. 

Option 2: Bookkeeping with QuickBooks Self-Employed Tutorial. If you need bookkeeping software, this one is for you. Note: I don't love Quickbooks, it's just the industry standard, and that's why my tutorial is on it. Other softwares you can try are Wave (free, but hiring help may be worth it), Xero, Sage, and Freshbooks. These are just a few of many.