I need some computer upgrade suggestions?

Your CPUs are fine. Put the maximum amount of RAM your motherboard will support in the PC. If possible, upgrade your video card too. But why would you want to use a PC from 2001 for gaming? This thing is ancient. A machine with 256 MB is really old, you might have a hard time trying to find more RAM for it. And other upgrade components for that matter. Computers are not like cars, you can't really upgrade a 10-year-old machine and see a huge increase in performance without replacing just about everything. Technology has changed too much in the past 10 years. Newer games perform a lot better on newer hardware. If you don't want to build your own gaming machine (which are the best), then invest in a new computer, and use this old Dell for basic computer tasks, like surfing the Web and word processing, or old PC games from this era (late '90s-early 00s)