Hi - if you are considering a sewing machine, look for one that will do the basics, unless you plan on getting into sewing in a big way. You can get all sorts of extras on a sewing machine, but for someone just learning, you really don't need all that. I would recommend you go with a new, rather than used machine. I see them at Walmart that sell for around $125 - $150 that will do everything you will need. It should come with an instruction book that will guide you in threading, setting tension, stitch length, etc.
If you can find a basic pattern in a pattern book, the pattern will have step by step instructions from cutting out the pattern pieces to the finished item. Start out with something simple, and use inexpensive fabric. That way if you mess it up, you don't have a lot of money invested. If the fabric you choose is 100% to 50% cotton, you should prewash & press the fabric before cutting out your pieces because of possible shrinkage.
It's best if you have someone to help you in the beginning, but if you can't find anyone, you can teach yourself. Just read and follow instructions, and be ready for lots of trial and error.