You want a suit, not a blazer. A suit is a matching jacket and pant. A blazer is just a jacket that can be matched to a variety of pants. Charcoal or dark grey single breasted, two button suit is pretty versatile and is prob what i'd recommend for a first suit. Get it tailored so that the sleeves are slightly above your bottom thumb joint, and so that the pants have zero to a half break so that it doesn't look as cheap. The dress shirt in general should be light colored. White or conservative pastel colors, dark shirts are tacky. Slim fit if your frame can support it. If you're wearing cheap clothes, having them at least fit well helps immensely. Ties should work with the shirt. Dont do matchy matchy, but complementary colors works well, or a significantly lighter/darker version of the color on your shirt will work.