Hi Rakesh.
Rather than selling in dairies you should consider selling your milk by yourself in your town and the nearby towns.
If you are planning to start with 100 buffaloes then purchase your buffaloes in three stages viz.
First at the start, take 35 buffaloes then after 4 months from first purchase again take 35 buffaloes and after 8 months from first purchase take remaining 30 buffaloes.
Reason behind this is that you will get consistent milk supply from your buffaloes throughout the year.
Buffaloes lactation or milking period tends to be less than cow but considering the more demand and better pricing buffaloes are profitable.
For marketing just register a dairy firm, give it a good name according to your location.
Then establish small counter based shops in the towns you wish to supply your milk.
For primary advertising you can advertise in local newspaper and you can also do a free one time door-step delivery to your target costumers.
This is a best method i have learned from my experience.
I own 60 murrah buffaloes and 40 hf cows.
I have myself did the marketing this way and today i get a rate of rs60 for buffalo milk and rs 45 for cow milk.
And mostly important, never compromise with your quality.
Best luck for your dairy establishment.