ITA, Clothing Construction classes are a GREAT way to start....also try taking apart pieces you already own that you don't care about anymore (seam rippers are key--scissors can destroy the cut of an item) and piece them back together in ways you do like. This will help get you started with how you like items to fit. If you want to be good, you need to approach it like a class/topic you enjoy--study, study, study everywhere you go. Analyze outfits on strangers (just be discreet!) and ask yourself: Would their pants look better if they let the hem down another half inch? Would the shirt look better if it were taken in on the sides and had pearl buttons?
Look into patterns in fabric stores. If I do choose to use a pattern, I'll usually buy a couple and use the bodice from one pattern with the skirt from another pattern, and I no longer follow all the steps, as the cut and fit of most patterns are extremely outdated (high waists, lots of pleats). I usually do follow where patterns say to put in darts because those are necessary for shape, but I don't do them to a point, I kind of round them out a bit. My mom sewed a lot when she was younger and my aunt is an AMAZING seamstress (I hope one day I can be at her level), she makes all kinds of Anthropologie-esque clothes from part vintage clothing and part fabric remnants.
I was selling clothing I'd made in a store downtown, but the guy who owned it started selling cheaper clothing from Miami as opposed to the Seven jeans and BCBG items he HAD been selling, so my prices started to look astronomical in comparison. He makes more profit from the Miami-based stuff, and it's still hella cute so I can't blame him, but I was living my DREAM--selling stuff I had made and seeing girls in MY DESIGNS....I will try to post some pics of a few of my items on my MUA account (I am so inept at putting them into posts!) later this week if you wanna check it out.
And I'm always around if you want to PM me with questions!