Level 3? Should be around 4 or 5M, I think.
I myself do not use the stretching, but do hard cardio & practice. Friendlies are good training too. You will go through a surprising number of greens (and some reds too, injuries will occur)
The faster trainers gain about a cone a green pack. 75 cones is a star. I don't have a calculator handy, and never really did that sort of math with timing. I usually figure how many greens I want to spend and train until they are gone.