hi Overclocking is done by raising the frontbus speed in the bios , i don't now your board so i can't tell you where to look. About the memory , The 2 most used are called pc100 or pc133 , this is a indication to what the ram can take if the FSB is raised , when raising the FSB you also raise the other devices mhz like pci/agp
If you want to get the max out of your cpu then go for the best merory/price
Just start upping the FSB in little steps and see where it ends , Then you can adjust/replace the things that's holding you back.You can get whatever speed you want but it costs a lot of time and money.