The Kareri Lake Trek is a good step up from Dharamsala's shorter walks, climbing through pine forest, village country, and open Dhauladhar scenery to a small glacial lake. It is popular because it gives you a real Himalayan overnight feel without committing to a long expedition.
Conditions still matter. The trail can be slippery after rain and snow changes the character of the upper section, so go with current local advice, proper shoes, and a realistic plan for getting back to Dharamsala or McLeod Ganj.