That depends on where exactly you want to be. If you want a peaceful getaway, far from from the busy life, I would suggest places like Lachung, Cherrapunjee, Dalhousie etc and if you want to get aquainted with different people of different cultures, I think Jaipur, Udaipur, Assam etc are fine places.
Solo trip is best choice should travel at least once in a life. Where you can learn new things by yourself.
Here are best places for solo trip.
1. Shimla
2.Goa
3.Mumbai
4. Alleppey
5.Kutch
If you're looking for a place out of the tourist radar, a place that offers a majestic view, serenity and closeness to nature, all at the same time, you should go to Shoja.
Dear User, If you love mountains and their beauty, try visiting some hill station.
If you intend to travel between May and October, specially in monsoon (July - August) visit Valley of Flowers.
Places like Hemkund Sahib, Badrinath, Mana etc can also be covered if you have time. Ideally speaking Valley of Flowers and Hemkund Sahib is on a trekking route, but you can take ponies or porter if you wish. One thing is for sure, natural beauty in this area is unparalleled. Exhaustive information on Valley of Flowers, how to reach there, nearby places to visit like Hemkund Sahib, Badrinath, Mana etc can be found on my blog Links as under: Valley of Flowers: https://voyagevedas.blogspot.com/2020/01/valley-of-flowers.html Hemkund Sahib:
https://voyagevedas.blogspot.com/2020/01/hemkund-sahib.html Badrinath:
https://voyagevedas.blogspot.com/2020/01/badrinath.html Mana:
https://voyagevedas.blogspot.com/2020/01/mana.html