Rush town hall level?

Rushing to 18 is fine, it puts you at the top of a bucket/bracket. I personally jumped straight from 15 to 18, and most people also decide to do this.

 

Rush to 18 since it makes your wall stronger, allies for training more troops at a time, increases your attack and all that Jazz. Just make sure all of your buildings and most of your research is done before going up to the 19-21 bracket. Do keep in mind brackets change depending on realm!