I've ridden a fair amount in the rain...both locally and on longer tours. We invested in decent rain gear (separate jacket and pants ) quite a few years ago, and it's still holding up well. The more money you have invested in rain gear, the less likely you'll need it...which is sorta par for the course with these sorts of things and which, in the long term, is not such a bad thing. Conversely, the reverse would probably be true too...buy cheap rain gear and you'll likely need to use it all the time. That's just the way things work

In my mind, the keys are:
Jacket...a bit heavier rather than real light material, for a bit of "structure", but still able to compress into a smaller carrying bag for trips; sealed zipper closures with a velcro overlap; full neck closure; adjustable straps on wrists and waist... to keep it from blowing in the wind; reflective strips (mine is Black with White strips); large enough to fit over riding jacket.
Pants...elastic leg openings with zipper/strap; "stirrup"straps to go over boots to keep legs from riding up: heat resistant material on inner lower leg areas that may contact pipes; pay special attention to fit, since too tight when sitting for longer periods of time is no fun, or a rip in the a** and wet butt is no fun either