I would begin with a light coating of 100% neatsfoot oil (not compound) and let that soak in for a day or two. I would then condition, working the conditioner in with fingers. If you don't make your own, some popular conditioners are Bick's 4, Blackrock, Aussie, and Lederbalsam. The key to longevity is to maintain the leather during use. For tack, that includes regular cleaning with saddle soap, applying conditioner as needed, and periodically oiling (but not over doing it).