You can't overclock with multiplier on that CPU as it is a locked CPU, and overclocking using the front side bus on that architecture is not recommended unless you are a very advanced user, because it will affect the bus speeds of everything else on the system as well. That is likely to cause major problems and instabilities. Besides which, overclocking THAT generation of CPU is not going to give you an increase of performance that will help improve your gaming enough to not still be a major bottleneck with that RX 460.
You need a newer platform.