I want to start a MLB regular betting routine again

[StarRain]

Hello guys, I was a huge sports betting fan a few years ago. However, due to the lack of BR management skill and a bad run of luck I decided to quit it. Now I am fortunate enough to maintain a stable extra income from poker so I want to start this over with a good discipline. What's the most profitable line do pro bettors put their money on? (Spread, Money Line, or combined runs?). How much $ per unit and how many units a day for a $5000 roll, for example? How much % do a average pro bettor expect to earn over a monthly basis? Sorry about all those rookie questions, thanks for any responses