Can I limit the amount of space itunes match uses on my iphone?
This is not possible. iTunes Match will continue to fill up your storage space as you download tracks locally on the phone through it. I believe it will trim songs once the space is full, to clear off the least-played material.

If you would like, you can manage your storage in a few ways:


Go to Settings > General > Usage > Music. Here you can clear all downloaded music.
Go to the Music app. Locate downloaded material and swipe across artists, albums or songs to remove them from your local storage.