Hey Santhosh! I loved the true traveller spirit in you. Kasol is one of the best place to go for a solo trip. Kheerganga is an easy trek and can be done even by a beginner. Stay at Tosh or Challal for a much local experience.
Stay in Pink Floyd Cafe in Tosh. It provides splendid views. Also you can start your trek from Tosh itself for Kheerganga. Manikaran you can visit on you way to tosh from Kasol. For more details, you can check my blog somyarakshit.com. I have mentioned all the details in particular there.