What is the best SUV to purchase that is air tight. we live on gravel and the dust just pours into our 2017 Equinox!
You're not going to be able to buy an airtight vehicle. That would be dangerous for multiple reasons. There are a few possible explanations for dust "pouring in" to your Equinox, such as loose door seals or a loose or damaged cabin air filter, but the biggest source of dust is almost certainly opening the doors after stopping.
When you have just stopped, a cloud of dust will be surrounding the car. Opening the door while that dust is still airborne will pull some of it into the vehicle.
You don't explain why you think this is a problem specific to this model. More specifics would be helpful. Do you run the air conditioner in fresh air mode, which draws in lots of outside air? Do you see specific places where lots of dust builds up, or is it more overall dustiness?