Unfortunately for gaming it's not going to be good and there is not much you can really do about that. With 12Gb of ram it means you are running in single channel mode which will lower performance especially where you are using an APU. APU graphics us system ram as vram as they lack dedicated vram and they perform better with faster ram. Installing a dual channel kist of DDR3L 1866(fastest ram the system supports) could give you a few extra FPS but a 8Gb kit is going to cost ~$60 and a 16Gb kit is ~$90. You could try just removing the 4Gb sodimm and replacing it with another 8Gb sodimm(~$55) but there's no guarantee it will play nicely with the existing 8Gb stick.
Replacing the HDD with an SSD can make a very noticeable difference in other things. The OS will boot much faster, programs will load faster, the system will feel snappier. A decent 250Gb sata SSD will run ~$80 500Gb ~$140.