Overclocking a laptop is not recommended. The design of most laptops does not allow for much more heat dissipation than a stock clocked (or even underclocked) CPU can handle. BIOS features which allow for overclocking are usually locked on laptops.
Adding ram may help but I would not expect by much. Your main handicap on that laptop is a lack of dedicated graphics, one which you cannot get around except by lowering your in game graphics settings to absolute minimums. Even then, I would not expect truely enjoyable gaming.
My $0.02 worth
Yes you are right! it is locked. So is it possible to upgrade from base point like Mobo, Processor, Integrated graphic chip-sets ?