I didn't hear you ask for advice, but here's my 2 cents, anyway. Take it for what it's worth.
GIRs go up, handicap goes down. It's a really simple equation. However, getting GIRs up from 15% typically requires fixing some swing issues first. A few lessons with a good teaching pro can likely get you going down the correct path. So, while working to correct those issues, practice, practice, practice short game.
I don't have a big game like some of the real players here. I'm more of the tortoise than the hare (so to speak) type of player. As a senior player now, with a somewhat respectable swing, I spend very little time on the range--maybe a half hour to an hour a week--but a LOT of time on chipping, pitching and putting. Every day. Partially because, my body can't take the pounding of buckets and buckets of balls anymore, but mostly because short game is the great equalizer to being competitive with guys half my age with twice my strength. Everyone can't drive the ball 300 yards, but anyone can chip and putt well with enough practice and understanding of the proper technique.
I sometimes play with young studs who can blow their drives 80 yards past mine. But, more often than not, mine are in the fairway and nearly every one of them is playable. Can't always say that for the young guns I play with. Also, the importance of managing your game and the course can not be understated. Sometimes it takes awhile to realize this critical element.
For the record, my numbers are not impressive relative to a lot of more accomplished players. FWIW, my GIR average is about 49% and my up & down average (inside 30 yards) is near 40%. I continue to play from the blue tees, though it's a stretch for me in the winter temps or when the wind is blowing. With those numbers, I'm still presently sitting at a 5.0 index. So, I have no doubt that you can get to single digits with the right approach. Just do it!