What are song must have songs for any ipod.?

I have alot of songs on my ipod but I have 50$ which I'll spend on music from itunes. any suggestions, what are some must haves on any ipod. I don't like new rap, I like old though, and I don't like anything along the lines of panic at the disco or fall out boy. And no beatle songs or country. Thanks. MUST HAVES