Some suggestions for you:
[*] Create a great website
for your network, and promote it in all the usual ways (banner exchange, careful keyword choices, search engine submissions etc.)
your network to all the usual places, like SearchIRC, Netsplit.de etc.
[*] Try to find other people with small networks who might be interested in linking
to yours - not only do you all gain in size, but can make yourselves into an international network too! Alternatively, try getting your server(s) linked to a larger network. (Obviously, there will have to be some give and take in the negotiations, and compatible ircd's...)
[*] Ask all your friends to tell all their friends on all the other networks that they're on. Encourage them to set up their own channels
on your server(s), for their own friends from elsewhere. Remember, the "snowball effect" is your friend! Since mIRC has multiserver, joining multiple networks is easy.
[*] Remember that you can promote your network in the real world
too! Put notices up in your workplace/school/local pub explaining what the network is for and inviting people to join you online sometime.
Hope this helps