A great starting point for me was reddit.com/r/malefashionadvice (and the associated wiki)
Some advice: focus, above all, on fit. Learn what each of the basic garments should fit like for your body type. Even the most basic budget wardrobe tailored to fit well will look great compared to expensive but unfitting clothes. Then focus on fabric quality, color combinations, and experimenting with your own styles (pinterest is great for exploring this).
Good luck!