newcleardawn has great ideas. I'd say that if you could, its always good to learn a bit of sewing even if its only by hand. its great for hemming pants that fit but are too long, adding more space for clothes that almost fit, etc. you can usually pick up basic sewing supplies from dollar stores and get cheap fabric at thrift stores. Ive been using the same piece of fabric to make alterations for a few years now and it only cost a couple bucks.
if youre interested, having at least a few small and large needles is a good start (multiple in case of needles breaking), sewing scissors, a couple spools of thread (I suggest at least one spool of black and white since that's usually what I use the most, plus other common colors) and any fabric that piques your interest. sometimes thrift stores carry sewing machines if you decide to get one and most thrift stores will let you check to see if it still works before you buy it.