The way that you know what ram to buy for your computer needs is by checking your computers memory usage in the Windows Task Manager area. You have to right click to the taskbar and choose task manager there.
The way that you can make your computer run faster without paying for it is simple.
The things people can try are to delete programs that are not in use.
How many run at startup, run fewer programs at the same time, clean up the hard disk, restart your computer regularly turn off visual effects, and change the size of your virtual memory.