Personally I think
Dots and Loops and Mars Audiic Quintet are their least good LPs, but there you go.

Cobra and Phases Group... is my fave, but many find it too long and overly complex.

Most people seem to like Emperor Tomato Ketchup, so maybe start there. And for early dronerock Stereolab, you can't go wrong with the Refried Ectoplasm compilation.

good luck!