well, you came to the right place as far as learning how things work. First things first, if you are serious about a clothing line, consider educating yourself. 9 times out of 10 there will not be someone to hold your hand through the printing process and you will have to rely on your own motivation to push forward and learn more. I think you need to ask yourself a few questions before you start making shirts. One thing i think might help put this in perspective: Would you be willing to perform the routine maintenance on your own car? oil change, filter changes, bulbs..fuses..? If you are thinking to yourself "what does that have to do with anything?" or "no, i wouldn't think about doing that" then odds are you should save your time and money and maybe figure out what might really interest you like the general design aspect and artwork.
Another couple things you might want to think about: how much time are you willing to sacrifice? Money? How about space? Starting a clothing line will cost you thousands of dollars if you ever want to make real money. That's just the way it is.
If none of this has detoured your decision at all then the first thing i would suggest purchasing is an instructional dvd or book that explains the process in detail. I would suggest a DVD because it's hard to make sense of the screen printing process without a visual to back it up.
make use of the links to websites on the side of the home page on this site. I live about 30 min. from the Vancouver, WA silkscreeningsupplies.com location so i get all my stuff there. Check it out.
Hope this all helps!