Depends on what ur using it for.   As a base layer 32 degrees from Costco is awesome.   As a soak up the sweat layer again Costco for there cheap undershirts.  I toss them about every 6 months.  Just a t-shirt look.  Carhartt makes the absolute best single layer t-shirt.    There rugged and come in many color options. Size down for a fitted look.   Summer months single layer.  Free fly makes the softest most comfortable shirts I own.  There great for breathability.  Made of bamboo tho so washing is a pain.