Im a single mother with 2 dependants, 1 job...best way to fill out my w2...only claim 1 dependant to get the most back at the end of the year?

The way to get the most back at the end of the year is to claim zero exemptions. For every exemption you claim, you get less at the end of the year and more in your paycheck.

The new W-4 form for 2020 doesn't use allowances anymore, so you no longer "claim 1" or any other number of allowances. The new form works differently. Use the Tax Withholding Estimator on the IRS web site to figure out what to put on your W-4 form. It will let you adjust your withholding to get the approximate refund amount that you want.

Tax Withholding Estimator