As much as you may say you will only ever have one lens...you will get another. Once you pop, you won't stop. Trust me. I should know, I started out with one lens...I'm now at five, and I still desperately want at least three more. So do the smart thing, realize that there will never be that one do-it-all lens, and buy the best lenses for each of your anticipated shooting conditions. Buy a landscape lens, buy a portrait lens. Buy a lens for macro, buy a lens for wildlife. Buy a lens for low light, buy a lens for fast action. But don't buy a lens thinking it will do all of these--or even some of these--remotely well. Because it doesn't exist, and even if it somehow magically did, it would cost more than what it would cost to buy lenses designed for each specific purpose.


That said, you don't specify the kind of camera body you have, nor do you specify your budget or any other relevant parameters besides "portrait/landscape" work. So I can't provide any recommendations.