How much do you normally spend on supplements per month?
I think your question may be to general, because the supplements regimen varies by stage of training and what stage of competition you are in.
If you are just training to train and are looking for a way to cut weight and increase strength then I think $75-$200 a month is about right.
If you are looking to compete, are focused on cutting weight, adding strength, and muscle recovery then you would be looking at $125-$250 depending on how serious you get.
Me personally, not training for MMA, but getting back in shape after being 6' 2" 273, I spend about $250 a month.
One other thing, I see so many people on different forums (I mountain bike as well, and have friends who body build) ask what other people recommend. The reality is that the information that they got is something they may have heard or picked up over time, or worse got from the guy at GNC who makes $10 an hour. I am not saying that some of the things are correct, or that I am even correct, but be careful and do your research. The number one thing I see is people taking multiple supplements from several companies, because it worked for John and Mike, etc. You get the point.
Look for supplements that meet the highest level of testing available, are certified to not contain banned substances, and are meant to work together.
Just my first post and my .02.