Studying different sports may seem like developing your mindset according to the op, but to me I prefer focusing on football sports because following up different sports makes me lose focus. Football is one of the best among all, very seamless, effortlessly, tiredless and interesting to predic and analise than any other sport. So studying others sport may develop mindset but in other hands make a person lose focused from my own perspective.
You can decide to focus all your attention on one sport then become good at it or you decide to study different sport that increases your knowledge on the different sports and might help you when you're gambling. There are people that can be playing different sport yet they aren't making as much money as someone that focus on only one sport. While gambling what matters is if you're making money when that's your purpose of gambling or having fun if you're gambling for entertainment. It doesn't matter if you're playing different games or only focusing on one. You'll have to decide and do what's working for you and not minding what's working for others or what others are saying. Your progress and success should be your only concern.