Search for throttle and you'll find some past discussions. I've tried a number of them including the "terminal commands" with varying results. The closest program to something simple was Entonnoir. It pretty much worked to throttle Port 80 - Internet download. And it was simple and free so I would try that.
I really needed something to throttle APP Store and Software update, which evidently, can use several different ports and was found to to be virtually impossible to reliably throttle. Someday mabey Apple will figure out that some of us have to SHARE bandwidth, especially in an office environment, and feature the ability to throttle the APP store. I noticed Dropbox does, and it is a welcomed feature.