Plan and decide your destination well in advance and do bookings of hotels and transport before you start travel. That way you can get heavy discounts.
Plan your transport mode perfectly and prefer state government transport as it is reliable and cheap. Sharing Taxi is another option to save some money.
Hire bike or scooter for local sightseeing from local service providers. Cabs can drain your budget fast. And travelling by two wheeler gives you freedom to explore more.
If you are fit enough to walk around and explore it can save lots of bucks for you. It is very exciting to explore local destinations on foot.
Prefer Homestays on hotels, as homestays are cheap and gives you option to talk to locals and explore more around your favourite destination.
Always try to eat at local dhabas and shops. this way you can enjoy fresh and local food at reasonable price and reduce your budget while travelling Solo to mountains.