Depends on what type of gainer you are. Some big posters and big gainers here on PEGym gained nothing in 3 months then went to gain inches in the 4th-6th months.
You'd be unlucky to see absolutely no gains within about 4-5 months but some people do need that time before they actually gain.
And some gain length quicker, some gain girth quicker. I'd say its more common to gain length quicker. In 6 months I gained loads of length, but absolutely no girth.
No matter what you gain, dont start upping the intenisty too soon if you aren't gaining as quick as you'd like, be disciplined and keep up the optimism and results will come when your body is ready for them

good luck