It's a reasonably interesting manga, but some of the fashion tips are pretty iffy. It's only one style that the author seems to emphasize at first, and it doesn't suit all people or even most occasions necessarily. Plus, the author doesn't even get into the most important part of looking good: hair (including facial hair) and physique. You can use fashion tricks to emphasize or conceal aspects of your body sure, but to really look good, having good hair and a fit body's the most important part, imo.
Plus, wearing too much monochrome can be pretty boring, and sooner or later you have to learn which colors match your complexion and hair and eye colors.
And the last thing to consider is that fashion doesn't necessarily do anything about your personality, or any potential lack of it. No matter how sharply dressed you are, if you're just plain boring (or worse, rude) a sharp jacket with great pants and shiny shoes isn't going to help. If you're hot and fun, even if you have mussed up hair, five o'clock shadow, and you're lounging around in a tracksuit, people will always want to be near you.
Whatever you wear, you'll make it look good by being you. Thankfully for this main character, he's a good looking and fun guy, even if it's in a hapless, approachable way.