I am using Google sheets to track ins and outs of money in my business. But what should I definitely do, and not do?
OK, serious answer here.
I'm a programmer and I sell products.
You want to keep a table for inventory and sales at the very least. Each table breaks down the respective transactions into their smallest components. For example, I track item price, tax, fees, insurance, shipping vouchers, shipping cost, refunds, etc. Then at the end of the year (or tax period), all you really have to do is sum up some rows/columns.
Now I over complicated this and did it in SQL Server with some fancy calculations to calculate item cost on the fly to determine a gain/loss on every sale and print out price sheets and a ton of other things. But you can still do the core functionality (how much did I make this year, how much tax do I owe, etc) with Excel or another spreadsheet.
You definitely want to keep a box with all of your receipts and invoices. And you definitely want to keep a backup of your spreadsheet on CD/SSD/paper or something. Just in case because the IRS can audit you a few years back. May be naive here but I expect an audit isn't such a horror story for people that A) aren't immediately hostile towards government and B) are organized enough to prove profits/losses.
I'm not familiar with Wave. You can use any spreadsheet program though. Excel, Lotus, OO Calc, Google Sheets, etc. Or notebook paper if you have the time to do the calculations yourself.