The commercial glider rating allows you to be paid for giving glider rides. Although the pay may cover your gas to get to the airport. It counts as total flight time so a portion will help towards additional rating requirements. I recommend getting a glider tow pilot endorsement as well. I built a handful of hours that way. Flying gliders is a lot of fun but using it to reach your airline goals is simply just a weekend sideline gig, logging a couple dozen hours a year!