I'm a bit late, but I've had experince with introducing males to male, and females to females.....here is what happened with me:
Jasper And Digit(m/m)
There was barely any fighting, the first day they "agrued" a little bit, but nothing more than chasing and a little nipping, no blood, only a tiny tiny bit of fur. They were introduced when both were almost 3 months old. To this day, they get along GREAT. They were in the cage together, the same day I got both of them. they've been together a year and 4 months.
Moose, Mocha and Espresso(m/m/m)
Moose was the agressier out of the three. He gave Espresso a few nips, and a bloody ear. Mocha just lost some fur, the others really didn't fight back. it took me about a week to get them together where I could trust them. Moch and Espresso were 3 months, almost 4. Moose was almost 5 months old. They get along GREAT now, and have been together for 4 months, and have been no problems.
Naomi and Danica(f/f)
My easiest introduction, by far. Both girls were only about 10 days away from being 5 months old. They never met before, are not related, from two different breeders. It was litearlly, love at first site. I put them together the same day, and minutes later, they were together, cuddling. I had NO fighting, no chasing, no niping, nothing. Everything went fine. I was actually pretty amazed that things went this well, beings they are females, and both are "older". They've been together a week today, and still there haven't been any problems at all between them. They act like they are long lost sisters, or like they've been together since day 1. (attached is a picture of them, just after I put them together)