The Parlay is a positive progression system. When using it you must "pyramid" your profits.
You should use the Parlay in combination with the basic strategy.
When using the Parlay system, you must double your initial bet after every win. If you lose you have to go back to your initial bet.
Let’s imagine you bet $10. If you have won, your next bet will be $20 (your original bet + your win). If you win again your bet will be $20+$20= $40 and so on. If you have lost, you must return to your original bet. The sequence is as follows:
If you want to use the Parlay system you’d better set a maximum bet limit not to go broke in the end.