I have just the original Everquest 2 with no expansions or anything, will I still be able to run the emulator or do I have to go out and purchase the expansion packs?

You still still be able to run the emulator. It goes off the game updates not expansions. Like when you download the latest update your eq2 client has all the features for all the expansions still, and it's the server that reads your account and disables the content down to your expansions.
Summary in short: Yes you can use it still.

Thanks for the answer raz