Consider wearing a grey crew-neck t-shirt and grey sweatpants for an easy-to-create look. White high top sneakers are a fail-safe footwear style here that's also full of personality.
Grey Crew-neck T-shirt with White High Top Sneakers Outfits For Men
A grey crew-neck t-shirt and navy shorts are a pairing that every sartorial-savvy gent should have in his casual rotation. For shoes, stick to a more casual route with a pair of white high top sneakers.
This getup with a grey crew-neck t-shirt and black jeans isn't super hard to pull off and is easy to adapt according to circumstances. Take your getup in a more casual direction by finishing with white high top sneakers.