My opinion is it depends on you situtation. I think usually it cheaper
and perhaps faster to get the power rating and then and the glider
rating. The exception is if you have a good soaring/gliding club
nearby where you can exchange your time for cost. It may take longer
learning to fly at a club but the cost for getting the glider rating
may be very low.

If you are going to do it strictly through commecial operations then
learning to fly power 1st usually makes the most econmic sense. After
you have your power rating you can add the glider rating in probably
less than a week.

Brian