Well the best time to visit would be after march since now it will be extremely cold. Also known as the valley of flowers, Post march is the ideal time to visit the valley.
Hey Syed, Auli is an awesome hill station and yes you will thoroughly enjoyed enjoy it solo ... It will be great if you have a companion with you ... Places to see are :- Mana Village the last Village of india is nearby to Auli .... You can also visit Joshimath and witness lots of trekkers dre as it is the starting point of many treks .... Also Badrinath shrine is also near to Auli ... You can also visit Tapta kund and Panch shilas and take a bath in hot water spring dre ... All these places can be visited on a daily basis as it is 50 Kms from Auli ... And at the time of christmas it will all be snowing and superb ... So have a great journey ... Happy Travelling Bro !!!
If you are planning a solo trip than it'a all your decision but it would be best in your interest that you take a partner around. And please refrain from going in this winter, it will not be that worth and most of locations will be blocked. Happy travelling!!