Avoid monsoon.
If you have your own car,you can travel anywhere if you have guts and confidence in driving seat.
google is there to solve all your travel route worries.
I have planned such a trip in 2018. You can start from Pathankot via Manali. after traversing , you can rent a vehicle of your preference and head towards Spiti, there you can stay at Kaza. from there you can go to Leh via zhanskar. finally to ladakh
It does not require a VISA but if you have your own vehicle, it costs you an amount and that keeps on changing, check the Bhutan tourism website before you make a visit!