I see nothing wrong in your screenshot. The rendering is very noisy, that's true, but what do you expect from 1 minute render on supposedly not very powerful machine? Render stats shows 35% noise level and that is what you get. You need either let it render for significantly longer, or enable real-time AI denoiser in render settings. As Tom already mentioned, adding more RAM won't speedup the rendering, nor it will increase image quality. The only thing that would affect the speed from hardware point of view, is to change current CPU to more powerful one. If you can't do that, then try to optimise the scene, reduce complexity of materials, look for more efficient lighting setup, or... simply let it render for longer time period.