Totally agree with Nathan, that 30mm is a beast. Honestly, if you look at the MTF charts for the Sigma 30mm f/1.4 DC DN Contemporary Sony E, it punches way above its weight class. But since you mentioned landscapes too, you might find the 30mm (which is like 45mm full frame equiv) a bit tight. If you want more versatility within that $500 limit, you should check out the Sigma 18-50mm f/2.8 DC DN Contemporary Sony E. Its basically the ultimate budget zoom for APS-C right now.

• Sigma 18-50mm f/2.8: Pros are the constant aperture and its tiny size (only 290g). Cons: it relies a lot on software correction for barrel distortion at the 18mm end.
• Viltrox AF 13mm f/1.4 E Sony E: This is a sleeper hit for landscapes. Technically impressive with 14 elements and almost zero coma, which is rare at this price point. Great for astro too. If you do mostly portraits, stick with the Sigma prime Nathan suggested for that f/1.4 bokeh, but for a mix of both, that 18-50mm is hard to beat for the price/performance ratio. It covers almost everything you need.

I've been happy with the Sigma 30mm f/1.4. Sharp wide open, good for portraits. Chromatic aberration is present, but easily corrected in post. Got mine used for $280; a steal for the image quality.