whether i have to buy GS150 suzuki bike or suggest any other bikes with good mileage with good engine capacity,no maintainence,high speed

You can buy this bike if you like it however, if you can further give your budget ie price band then can give you better suggestion. Regarding mileage but with high capacity.. there is no good match.

You can't expect mileage from high capacity bikes. So let us know what is your priority speed and power or mileage !!