Slowly add time. For instance splitting your jelqing up, doing 5 minutes at a low intensity (20-40%) and 5 minutes at a high intensity (60-80%). The low intensity will aim for length while the high for girth. Add 1 minute of jelqing to each, every two weeks until you hit the 10 minutes. This will give you a total of 20 minutes, which is build up slowly and has the biggest chance of giving you both length and girth gains.
For stretching I would add 30 seconds to each direction, every 2 two weeks until you hit 3 minutes to each direction. The 3 minute long stretches have I been doing for 15 months now, with excellent results.
Start clamping when you don’t are a newbie anymore, which means start it after 3 consistent months of the newbie routine.