What is the best way to get from Gatwick airport to inner city London?

I know there are several options like the Gatwick express train, Southern trains, first capitol, easy bus, and the express coach. I'm hesitant to buy a train ticket as i do not know how big the airport is and how long it might take to get my luggage once I land. Generally speaking what is a quick and cost effective means of traveling from Gatwick airport to inner city London? What would you do?