Server donation plugin help!

Hi I am using the buycraft donation plugin for my server but I have encountered a problem and I cannot find a solution to it!Its not a big deal and all but its starting to annoy me.So I am wondering how I can make it so someone can purchase the following
Mcmmo
In-game money
I don't know how to make it so they can buy a certain amount for each, the amount being what I have to offer in the shop whether its 25,50,or 100(mcmmo or in-game money).I also do not know how to make it so when they purchase the rank they automatically get a prefix I want the prefix to be [Donator] in pink just don't know how to do it! please help!

 

have you tried another plugin for your donations? buycraft is great to use, but i felt that the enjin donationcraft was easier to use my server, my users had a vote and majority of them prefered the other one.