Please guide me on improving my rating on Google

My site currently has a score of 70. This is a decent score, I know, but I need to improve it. I have set myself the goal of getting my site performance up to 85 or above, but I don't know how to get there. Does anyone have any real advice that can help me as I seek to improve my site's score? I have made a goal for myself but I really don't know how to reach that goal and I need some advice that I can follow that will help me succeed at reaching my goal. How can I tweak my site to get the score up?

My web site is - http://www.maxbetsbonuscode.co.uk/

Here is the rating, so please help me out with getting it up to 85 will be extremely thankful to you guys -

http://i60.tinypic.com/2rqfsbp.jpg

Even the speed is as good as one could wish for -

http://i59.tinypic.com/2dksqp.jpg