Random misfire

I have a 2000 Alero, 2.4L.

It is misfiring bad. My roommate has changed the spark plugs and coil tower. Next are the coils. I also noticed I have a bad oil leak there is leaking on my plugs. Before I just keep throwing money at it, what else should I check? I don't know much about cars and I don't really have the money to take it into a shop, so I just have my buddy working on it when he has the time.

thanks!