Hey, Grant, welcome to the forum.
Here's a Lincoln reference for you:http://www.lincolnelectric.com/assets/g ... /c4200.pdf
And here's the boil-down answer to your question, from page 28:
The rate of flow for short-circuiting transfer with either CO2 or a mixed shielding gas is usually 25 - 30 cfh, (12-17 L/min). For globular transfer or axial spray transfer, the flow rate is nominally set at 35 - 50 cfh (17 - 21 L/min).
From the picture at the Lincoln site, the 210MP comes with a regulator that shows cylinder pressure on the right hand gauge and delivery pressure on the left hand gauge. That will do the job, although many people prefer a flow meter.
Just in case it's helpful, here's a link to a weld settings calculator:https://www.millerwelds.com/resources/w ... calculator
What kind of projects do you have in mind?