Wait for Reviews
In most cases you can tell the quality of the DLC content within the first release or two. If you want to spend your money wisely, you should wait to see what the early reviews of the DLC content are.
This will help you decide if it is something worth paying for, or if it's not going to match up to $50 worth of content.
By next week you should have a good idea about what the content looks like, how it performs and what other gamers think about it.