I spent my younger years on the rodeo circuit owned lots of leather goods... then got into traditional archery - more leather items. Married a barrel racer and acquired more leather goods. Spent 13 years as a baseball dad to a kid that played about every position - many gloves... During my son's 4 years in high school ball, I was the unofficial glove guy - relaced a few each year, reconditioned, etc. Baseball gloves are the worst too - they are in the dirt all day every day, get wet, sweaty, etc.....
Over the years I have acquired a 5 gallon bucket slap full of leather care products, and the best thing I ever used is Lexol leather conditioner in the spray on bottle you can get at most any auto parts store.
Many people use too much conditioner on leather - you don't have to over do it. Clean dirt off, spray on lexol wipe down - that's it. If it gets really bad, their cleaner works well also.
Most all leather conditioner products do work. I like Lexol cause it's light, the spray bottle makes it easy to use, and it doesn't over soften leather. MLB teams use it as well.