What you need to pack depends on where you are posted. Hence, the best thing to do is to know your place thoroughly. As suggested before, visit your place. You can actually start your formal attendance (हाजिरी) while visiting your center for the first time, take a few days’ leaves and come prepared as early as possible. In order to get your 2-year completion certificate, you require 233 days a year of attendance, so a few days wouldn't matter much in the long run. Also, you get to finish your posting earlier.
When I got my appointment letter, I searched for my posted site on Facebook and figured out Dr. Santosh works there; I contacted him and got his number. I found out that I had to live on rent nearby until the quarters got ready (which literally took over a year after my posting). It won't be much of a surprise that my travel checklist ended up being very long. I still cringe remembering how I had to pay a person's fare for my luggage when traveling on a bus from Dharan to Beltar.
Below is the checklist I used and usually use during travel. Feel free to modify it according to your needs.
Documents
Travel Aid
Appliances
Toiletries
Clothes
Others
Disclaimer: I travel heavy 😆