My daily uniform is a pair of Frye boots, Levi's jeans and a random solid color t-shirt. In colder weather I favor the classic M-65 field jacket, and as I've written elsewhere I drive a 20 year old Wrangler.
The people who need to know what I'm able to offer can still smell it on me and trust that it's real. And the people who are on the prowl for typical mark-markers just walk on past.
It's really more about how you carry yourself and interact with people than anything else. In my mind, whenever I see someone posed in front of a Lamborghini my first thought is to comment "Oh, how's your new valet job working out?".
Usually it's the people who spent beyond their means for a luxury item who want to show it off, so yes definitely avoid those.