This solid T-shirt works as a solo piece or under a button-down shirt.
Gildan (5-pack) Bulk Solid Heavy Cotton Short Sleeve Blank Tee T-Shirt S-XL
A crew neck design like this one works great for layering under jackets or hoodies.
150 Years of Major League Baseball | Gildan Men’s T-Shirt
The black shade is deep enough to look premium without being flashy.
The Incredibles Custom Mom Dad Family Birthday Boy Girl Customized RED T-Shirts
A nice touch is the multicolor ribbon trim inside the neck.
Customized Birthday boy Super Mario Bday Family Funny Cute matching T-Shirts
You will find that unisex adult sizing like this is a safe bet for online orders.