How to improve?

Hi, this might be a silly question but here goes nothing - I am a constant in the Sapphire league, always playing at the edge of the Ruby league. I level up but cannot keep that status for long. Now I am not going to blame Ninja Tommy and Tyzzon users (even though they are always there), and I do enjoy playing against better players ( since I can learn things). But do you have any advice on how not to fail every time I get to the Ruby?