The first thing you need is a graphics program so you can make your signatures. I think the 2 best are either Photoshop or Paintshop Pro. Personally, I use Photoshop.
There are a few graphics programs that are free, and probably the most advanced of those free programs is The Gimp. I have tried The Gimp and found it hard to work with, but that might be, because I'm used to Photoshop. The Gimp does have a lot of cool things about it, and like I said The Gimp is free. A full program of Photoshop is pretty expensive, even older versions still run you quite a bit of money. Photoshop Elements is pretty reasonable, (right around $100, maybe a little less), and Paintshop Pro is about the same price as Elements. Full Photoshop will cost you about $700 or more. Older versions might be $500.
You can download free trial versions of Photoshop Elements and Paint Shop Pro, which will allow you to use them for about a month. At least that way you'll get an idea of what they're like, and whether you'd want to purchase them. I think they're both a LOT easier to use than The Gimp, but like I said, The Gimp is free.