Those who have never been to the Himalayas or in Nilgiris or on any other mountain range, I can bet that they are missing something important in life. Even those who have been but not trekked a few miles through the jungle path they too are missing the touch of nature. If you are one who goes to the mountains and treks quite frequently, I call him/her most fortunate one. Commune with nature and see how your personality blooms. You become a better person.
It does not need much. A little money around Rs. 3,000/- to Rs. 4000/-, proper planning, a like minded friend, a nice camera, a rucksack with your personal clothes, jacket, sweaters, rain coat etc. Please keep a first aid box for any eventuality. Of course, you need to have an adventurous mind to explore unknown places and take the risk of getting stuck in an unknown terrain.
Instead of staying in hotels, the best option is to stay in Ashrams if these are available. It has two advantages, one is the location will be fabulous and the cost will be very very minimal. It depends on you how much donation you pay with pleasure.
There are so many beautiful places in India that too hardly treaded one that you can explore them for the next 20 years. The Himalayas from Arunachal Pradesh to Kashmir it has a long stretch of about 3000 k.m.. Do not just touch the place and go but stay overnight. Trek to little known places around collecting information through internet or local people.
After coming back from the trek, write a travelogue and upload photographs for others to enjoy. Even when writing the travelogue, you will yourself relive those wonderful days of itinerary. I assure you that you would receive interesting comments from the readers. This way not only you improve your writing skills but also you open up a constructive channel of communication.