Well. There are only 3 ways to build a network.
First one is the fast, the easiest and the cheapest - to use some ready solution like "ning" that you mentioned before.
The second one is to learn programming languages/technologies/tools and to build it from nothing by yourself. If you are new to web development, it will take a lot of time to learn all this staff and be sure, your first project will contain a lot of errors, but it can be a great expirience for you if you want to connect your life with web-programming.
And the third way to build a project you need is to hire an expirienced web developer team or find a company, which will do this for money.
I don't think there are any other options how to build a network