Yes, adding a second DIMM to not only allow your memory to run in dual channel, but to also increase the capacity, is probably not the worst idea especially considering the fact that it is relatively slow memory at only 2400mhz.
Really it depends on what the rest of your hardware consists of. What model is your CPU and motherboard? Graphics card and PSU?
Ryzen "likes" higher RAM frequencies, lower Cl and dual channel. Most are happiest at 3200MHz Cl14. Since you are using dedicated GPU, I would give 2400MHz RAM just a passing grade. CPU's IMC "natural" frequency is 2666MHz although it can go much higher.
When using IGPU, memory frequency demand is much higher of course. Under 3000MHz is not even worth considering.
CL14 memory isn't really a requirement to achieve advertised speeds like it was early on. Even CL16 3000/3200mhz sticks should be able to run at their advertised speeds on B450 and X470 boards so long as you have an updated BIOS.
If you have an A320, B350 or X370 board, then I'd probably try to find a CL14 kit (Specifically, CL14 when the sticks are 3000/3200mhz, because CL14 doesn't mean much at other speeds. At those speeds it means they are going to be B-die modules.)