Approximately 1 month you realize the effect so slowly (3kg increased). By Mega Mass I have about 20kg increased in one year, without thereby look fat. ;-)
Of course I also made 3 times a week and strength training changed my whole diet. Also playing a major role.
Now after 2 years, I finally reached my desired weight: 82kg !! :-)
My advice to all Hardgainer:
1.) 2-3 shakes per day!
2.) rice, potatoes, meat, fish, eat vegetables!
Drink 3) 1L milk per day!
4) peanuts in between!
If you follow the tips, you will jerk twitch increase. (For me it was the case)
I hope I could help you! ;-)