Which Lenses should I aim for? Sony a6700

Its my first camera, I bought with kit lens cuz I got a decent deal. I didn't have money to buy an aftermarket lens. Which lens should I aim to buy next? I do mostly street, landscapes and few portraits.

Currently on my mind I am planning to buy Sigma 18-50 f2.8 contemporary. something which will not break my bank. Are there any other better suggestions? This will be the first time I will be buying lens so I am worried I'll pick the wrong thing