I think October is a great month to travel anywhere because the weather is wonderful. You can check out the mainstream ones like Shimla and Rishikesh if you haven't already. Or go for something offbeat like Chitkul or Thirtan Valley
First start with Uttrakhand , because going in much cold place directly gives you troubke first visit places in Uttrakhand like -nainital , Haridwar or Rishikesh Rishikesh and naintal were best among these ..
and then further visit HP ..for further information for visiting Uttrakhand and most economical ways ..you can dm me