If you do much sewing for yourself I can't tell you how indispensable a dress form is. Sure you can try what your making on and pin it but that gets so tiring and if you ever plan on doing any original designs which include draping, well then you really have to buy one! The problem is they are very expensive. It's easy to find them used on Craigslist and I have seen a few in thrift shops and at flea markets. If you do buy one used it really should have one measurement that fits you and that is the high bust measurement, the area above your chest and going under the armpits. You also should never buy one that is bigger than you because as you can see you can pad it to fit perfectly. If your lucky you will find one that fits you perfectly.
This is my dress form that my husband bought for me when we were still dating and I was turning 23. It was a pretty extravagant gift at the time costing about 500 dollars if I remember correctly. It is a WOLF form, one of the best ones in the industry. You don't have to buy one this expensive, Singer makes an adjustable one that cost about 200 dollars. Now as you can see it is too small for me now. I guess I can blame those four kids for that ! I can pretend I'm still the same size or I can get realistic and drape my projects on a form that will actually resemble me. My high bust measurement is still the same as it was back then so all the form needs is a little padding.
You can find expensive kits on the internet for about 100$ or you can simply do it yourself like this:
Use an old bra that fits you if the form is too small in the bust line and pad it till it fills the bra. Measure to make sure you haven't overstuffed it!
Pad the waistline with batting. Buy the kind that comes in a roll like a sheet. Wrap it around the waist till you get the right size. I had to go from 26" to 28 1/2.
Buy one of those shaper tanks and pull it over. Adjust padding if you need to and double check your measurements. She looks a little lumpy to me but it should work. We'll see...