In order to save more files, you would need to increase your hard disk drive size. Hard drives may be purchased for very reasonable prices, and are very easy to install. RAM will not affect the number of files saved to your system.
I believe you are running out of disk space, since you want to save more files. You need to add or upgrade to a larger hard drive. Upgrading RAM only allows you to open up more programs at the same time. RAM memory does not actually store your files.