I've recently been absolutely obsessed with Uniqlo's oversized AIRism T-shirts. If you know anything about them, you'll know that there's a cult following for these because they're affordable at only $20 each. They're thick yet breathable and smooth, and the cut is fashion-forward. I like to alternate between these and custom-fitted T-shirts just to change things up or if I'm really in a hot climate like where I am in Malaysia. And I just have a bunch of these in different colors, and I just throw them into the luggage, and I'm good to go.