I want to move on, or want a new challenge. As long as you don't say anything bad about former company, everyone can understand you after better money. OR, you can say this place is more closer to your home.
我觉得在说“I am looking for better pay " 的同时,必须 千万 始终 前后 都不能忘记说“this position fits me better and I am sure I can make more contribution to your company".而且还要两眼放光地充满期待的样子。