Mr Creaze,
As others on here have eluded to, it can be a bit much for us mere mortals to calculate the square roots etc whilst flying, I simply included the Math in order to answer your question. Hopefully it explains why the Maneouvering Speed varies with weight.
Others have mentioned the best Turbulence Penetration Speed, and sticking to the colours on the ASI, which is all terrific advice.
My advice is to commit all of the limitations for your aircraft to memory, so that you can recall them when required, without the hassle and time to pull out the manual or find the placard and read it. Especially numbers such as Vne, Vno, Vbs, Turbulence Penetration, Maneouvering Speed, Flap and Gear Limitations, Best Rate and Best Angle of climb, Max Range Glide Speed, all of the Approach Speeds, and the like. It will make you a more confident flyer.