Everyone around me that I saw took gambling as a source of income become broke. They sold some of their belongings like TV, computer and some other things just because they are so much addicted. But luckily they have all recovered after they know that they are about to finish ruining their lives. Gambling is not a source of income. Anyone that think gambling is a source of income is foolish.
Reading through the title of the OP's post infact, already had me concluding the concept of taking gambling as a job or your major source of income. This is because having a range and a bulky one at that already suggests taking gambling more seriously than expected.
If gambling is really taken as a fun activity with a probable chance of winning then you shouldn't be soo fixated on even having a defined range which your profit must fall into, because the question would be your approach it things went sideways.