I am another supporter for Mohair. One thing that will help to prevent galls even when your cinch gets older is to wash it frequently. I use the power nozzle on my regular water hose to pressure wash most of the dirt and sweat away once every few days (but I ride a lot of horses every day), you may only need to do it once a month or so.
However, while mohair is great, this is actually my favorite cinch for the moment. Professional's Choice - Western Products - RCM
It's the only one I have found so far that doesn't wear horrible galls on any of my young horses.
Along the lines of what Churum mentioned about the baby powder on the latigo. You might want to avoid leather latigo straps. They require more care and will often get sticky, making it almost impossible to get your cinch as tight as it needs to be. I will only use the nylon latigos. They last longer, require less care, and are cheaper to replace.