You need an appropriate mix of protein and carbohydrate. I don't purport to know what that is for you, but:There's nothing fancy smancy about supplementing. I've decided to start lifting weights again, get back in shape and stay that way. An ordinary diet just doesn't provide everything I need at 55 to prepare for the workout and recovery from the workout.
I'm in my 50s and I run an average of 70 miles a week for cardio. I only do weight training 2x weekly. I want to be lean, but I want good core strength and do good work for my bones. My doctor has persuaded me that cardio is more important at my age than weight training is. You need to weight train too, but he wants me to focus on cardio.
I practice a "work week vegetarian" diet. M-F it's lots of fresh vegetables and legumes -- lentils, beans, etc. We have something with pork on Saturdays and something with beef on Sundays. A whole chicken which provides leftovers every now and then. Throw in some quinoa during the week (a complete protein), and you're covered M-F. For breakfast 3-4 days during the work week, I have a fresh fruit smoothie. Some citrus, some apples, some bananas, some strawberries or mangos in season (basically whatever you can get that's fresh)... Usually fills up a 40 oz glass and provides energy until lunch. Other days I have eggs. We keep a sourdough starter going year round and only eat bread we make -- no commercially-made bread allowed.
We generally buy beef and pork on the hoof locally in southern MD and we figure out a way to make it last for a year until we take another delivery.
I do drink a mix called "Accelerade" on longer endurance runs. I've used gels from time to time. If you're burning energy, you need carbs. This is a 4:1 carbohydrate/protein drink. All carbs need some protein to deliver energy to your cells. I find I don't need supplementation for weight training, but it only plays a supplemental part in my training regimen.