When you are developing a new system based on a new platform as Intel 12thgen and beyond, or AMD AM5 then you should probably use DDR5. It is not simply the case of sheer speed, but also about being future-proof. The bandwidth of DDR5 is higher, the power consumption is reduced, and DDR5 continues to become cheaper.
However, even without having a big amount of money, in the home country, there is a big price difference between DDR4 and DDR3, then that is still completely acceptable to use in gaming. The difference in the real world is not that monumental unless you are playing very CPU intensive games or are on a monitor with 300 or more FPS.