If a blue shirt & khakis is the boring uniform of business casual, its Luke Wilson off-hours equivalent is the untucked dress shirt & jeans.
Here's how to take this casual pairing from "Eh." to "Excuse me, is anyone sitting here?" with some easy adjustments.
Button down - An untucked traditional dress shirt, especially if it's a standard fit can look sloppy, opt instead for an actual casual button down; these really do exist I swear, it's not like the virgins waiting for you in heaven thing. Typically casual button downs posses a fit and print better suited for 'hanging out'.
Jeans - Even though the typical sartorial rules for pant breaks don't apply to jeans, there is such a thing as too long (no TWSS jokes please). If the denim starts to to buckle and bunch up to the knee or higher, that jagged silhouette is a sign your jeans have gone too far, literally.
Layer - Layering is the casual man's secret weapon, well that and ordering off the dollar menu. Even a simple, non logo emblazoned sporty zip up like the one above adds visual interest and can eliminate suspicions that you just rolled out of bed in your t-shirt.
Noggin - Men tend to update above the neck at an even slower clip than below. Exhibits A and B, glasses and hair style. If you've been wearing the same glasses for a few years now consider upgrading frames or getting contacts. Lastly, when it comes to your hair, even small changes can make a big difference like brushing your bangs to the side rather than having them lay limply across your entire forehead.