The best way to sell it is to clean it up, take good, clear pictures of the saddle from both sides, top, underside, front, and back, and include measurements of the tree if you don't know the size. If you don't know how to describe the rigging, then pictures of that will help as well. Without being able to provide information such as the type of saddle, tree size, and clear pictures then you likely won't be able to get nearly as much selling it online since folks would have to take a gamble on it. You'd have more luck if you could find a local buyer that can put their hands on it. If you can take them in good lighting on a proper saddle stand, then that's all the better.
I have a Tex Tan Hereford saddle that I'm casually trying to sell as well. It has some cracking similar to your saddle, and a couple of other cosmetic flaws so I have it listed at $200. I've only had a couple of interested buyers in the month or so I've been bumping the ads up, but I haven't been pushing it too hard.