I'm a 1st year business and have no idea how much I'm going to make. Is there a minimum amount I have to pay in quarterly taxes? Can I use my w-2 from 2018 to estimate?

I just started my self-employed business last month and I have no idea how much I'm going to make. I don't even know how to guess. Is there a minimum to send in for quarterly taxes? 

I thought I saw somewhere that I could use last year's tax numbers to avoid penalties. Does that only apply if I paid estimated taxes last year? I have my w-2 from the job I worked last year. Can I use those numbers? 

I have no idea what I'm doing. Any advice would be appreciated.