It doesn't matter where you go. What matters is, you go and learn from your experience and go again and again to tell people the exact same thing that I'm telling you right now.
P.S. Before my first solo trip I went solo to a pub :p P.P.S. This blog might help you:
https://www.gonimad.com/blog/orchestrate-your-solo-travel
For your solo trip you can try either the triund trek or kasol-kheerganga trek in Himachal Pradesh. Both these treks are easy and perfect for first timers.
Southern Part of India is quiet good, if you are planning to explore solo. There are lot of destinations like Coorg, Ooty, Kerala, Andaman, Pondicherry etc. If you are planning to go for a hill station Ooty is the best option. Go for a Ooty Package. You can book unique stays in Ooty and enjoy your time there. Check Out: https://www.funstay.in/list/Ooty/unique-stays