I did everything, i tried everything and im stuck because im trying to make my server have a mulitplier but it keeps saying the command is not found and will put my server under community even though i have the gather manager plugin where it's suppost to be.

So you pressed F1  and then typed the following :

gather.rate dispenser Wood 10 

and it says not found because it seems you're tpying it in normal chat and not in the F1 console.