That's a loaded question, but the simple answer is the best stretches are the ones that work for you and bring you growth.
Everyone will be a little different on what works, and what may have worked or is working for one brother may not work for you.
Have you read SRT?
Start with newbie stretches hitting all angles. Get the Lengthmaster if you can afford it so you can progressively increase your intensity if you are chasing length.
Get a Mityvac pump system if you are chasing girth and do 5x5x3.
I am sure other brothers will respond as well.