You want to keep a 5:1 or 5:1 ratio of females to males. With 25 females, given a choice, I'd start with 5 males or so. Too many any there will be a lot of competition for females.
As far as the garage goes, mine live in my garage out here in az. You should be fine, just watch temps and humidity.
With that number, it's going to be a while before you can feed your dragon off of your colony, but it's a start! Don't overspend on food, do some redearch and look at labels, and it's easy to keep it cheap.