If you can't sew a stitch the best way to get your wardrobe together is without question the wonderful world of the Thrift Store. This is also a great place to start to learn about sewing because it's much easier to learn to do small alterations and additions than to begin by wrestling patterns.

When thrifting train your self to see things with a creative eye. Even the male children should keep an eye out for treasures like velvet dresses as these can often be turned into, vests, tunics, and shirts with some careful application of scissors and imagination. Keep in mind that you may not find tons of great items every time you go. The best way to learn which stores consistently have wondrous bits and pieces is to go often. It can be frustrating at times but the only way to build up an impressive wardrobe on the cheap is to be persistent!

There are only three things you really need to take with you when starting out on a Thrifting Expedition:

Well, duh! Just take what you can afford. Watch out for places that have half price tags. These will change every week, and if something is a bit more than you want to pay now, it might be half price next week... if it's still there. It's always a gamble!
Some things can be altereted or worn in ways other than what was originally intended. Don't be afriad to experiment and try on.
An honest companion
If at all possible take someone whose fashion sense you admire and who will give an honest opinion. They are the best way learn what works and what doesn't... and your more experienced goth friend loves to go thrifting too!