You don't need to do a starter, but it will help reduce lag time and ensure that you're pitching a hefty amount of yeast. I'd agree that it's better to focus on temperature control and sanitation for your first batch and worry about starters later.
For your second batch, consider dry yeast. A bunch of us here (myself included) use it because a packet of the stuff contains a whole ton of yeast cells, and all you need to do to wake them up is rehydrate for about 15 minutes. It's also about 1/4 the cost of liquid, and there are some very good varieties available for clean tasting American or English beers. Don't take this as anything to worry about with the kit you just ordered, but simply as a way to make things a little easier and cheaper next time. Have fun.