The Sigma 30-mil F1.4 is a mighty all-round lens, and that is what you want from a lens, especially as a beginner. You can shoot products, portraits, and landscapes, cars, and street photography with this lens.
If you're looking for a fast, sharp lens that has incredible bokeh, a versatile focal length with tremendous autofocus and outstanding image quality whilst being significantly cheaper than its nearest competitor, then a Sigma 50mm f/1.2 DG DN Art might just be for you.