This is definitive proof that a long sleeve shirt and jeans look awesome when paired together in a casual outfit. Introduce black leather loafers to the equation for an instant style upgrade. This getup shows that dressing age-appropriately and looking stylish are not mutually exclusive things.
A long sleeve shirt looks especially nice when married with jeans. Why not take a dressier approach with shoes and introduce beige suede tassel loafers to the mix? As you're going from your 20s to your 30s, you want to start dressing like a grown man. If that's the case, ensembles like this are perfect as inspiration.