The only way a bubble level works is to have the car on a level surface.

A rough way is to use a framing square on the ground and measure the distance from it to the top and bottom of the wheel. ( Not the tire as there is a bulge at the bottom. ) The tire should be square to the ground or slightly tipped in at the top.

More importantly, the toe must be set as that will affect stability much more than camber / caster. To measure, use an angle or 1" square tube pressed against the tire. Be sure to place the material above the tire bulge but not so high as to cause the measuring tape to hit parts under the car.

Measure between the material in front and rear of the tire, they should be equal or up to 1/8" shorter at the front.