To answer your question, I think Bike Soul 2.0s are the lightest wheels you're going to able to get under $500 unless you can find something used.

However, losing weight and increasing your power output is the easiest way to get faster up hills. It's all about how many watts per kilograms you can sustain. The more the better. I'd say I'm pretty good on climbs because I only weight 135 pounds. However, I suck at flats or pulling because I'm a mediocre rider. I've seen many other riders that can drop me on climbs even though they probably weigh 40 pounds more than I do... It's because they can produce more watts than I can and hold it.