If you can't answer the question of what lens you need to buy, you are not ready to buy a new lens. You shouldn't buy a new lens until you reach the limits of what you're currently shooting with, and you understand why the lens is limiting you. Then you'll know what focal length and features are important to you and be able to make an informed decision for yourself. We can't answer the question of what lens to buy because we aren't you. It's that simple.
I disagree with this. It's the buyers prerogative whether or not they want a lens now or later. Buying when "ready" for a piece of equipment is an unnecessary deterrent with no applicable benefit. I bought a D5100 and returned it within a week and a half of ownership, and then waited over a month for the D7000 to be in stock. Never looked back. Waiting to be bottlenecked by your gear is something I would not advise doing. After all, it's just a camera lens and not a crotch rocket. All it takes is the identification of what focal lengths you use and then if you have the money for it, go for the best you can afford. Experienced photographers mock the inexperienced for having top of the line gear out of sheer arrogance or even jealousy, when in reality that's probably the best thing you can do. If you know you like photography, and you know it's something you are going to be serious about. Buy the best now. You save money in the end. I don't know why people recommend $300 tripods, but then recommend cheap equipment to put on it. Not you destin, but I have seen this here on the forum.
If I were to do it all over, I would not have bought the lenses I did. I'm 4 months into ownership, and I am already looking to upgrade my lenses. If I were to do it all over again, I would have spent the extra few hundred on much better lenses.