A crew neck design keeps the look minimal, which is perfect for layering.
Milwaukee Admirals 1977 IHL Hockey Tri-Blend Royal Heather T-Shirt
You will find that an unbranded shirt like this is hard to beat.
Gildan G640 Adult Softstyle T-Shirt Ringspun Cotton Crew Neck Plain T-Shirt
You will find the crew neck stretches just enough to slip on without hassle.
Gildan G640 Adult Softstyle T-Shirt Ringspun Cotton Crew Neck Plain T-Shirt
What I notice is the crew neck, which has a slight stretch for easy movement.
White T-Shirt Undershirts, 10-Pack, Best Cotton Undershirts, Stay-Tucked T-Shirt
A nice touch: the solid design means you can dress it up or down without effort.