2GBs of ram is a good idea. Not sure if its worth the cost of 4GBs. Yes if you can get it cheap enough. System is old however. You'll be better off only spending money on parts that carry over to a new system. Which DDR1 won't.
Thanks, for light gaming and some graphic work do you think it is worth buying another gig for $40-50 and waiting a few years to upgrade to a new system, or wait buy a new system in around a year when I can afford it?
For a rig that old, probably not. You need more then just ram. A faster CPU will help as well. Doesn't make sense to spend a bunch of money on ram, if you have to just throw it away when you buy a new rig.