Throwing the baseball will definitely make your arm stronger. Long toss is key for a strong arm. I was at 60 at the beginning of the fall off-season (2016) and I'm hitting 70+ on a regular basis now. The Jaeger throwing program was incredible for me. Get yourself a pair of J-Bands too, and do them EVERY day. Lifting would help your velo, but bodyweight exercises are also great especially if you don't have gym access like many people. Pushups, pullups, situps, etc. I would recommend alternating distance running days and sprint days (suicides are good for explosive power) as well. For lower body, do squats, squat jumps, lunges, and for core, planks are really good, if you do 60seconds each regular, left side, right side planks every day you'll be set (I have no idea what your fitness level is but you might want to go for two sets of the planks, six minutes total of planks a day). Good luck!