Speaking as a 50-something (I turn 54 on 6/13 in case anyone wants to shower me with expensive gifts), I really don't know what 50-somethings are supposed to wear. I'm skinny enough that I often have to shop in the young men's department to find clothes that fit; like there aren't enough guys with a waist size under 32" for the grownup men's department.
Fortunately I'm not that concerned about how lame I might appear. I found the Marc Anthony clothing line in Kohl's fits pretty well; I have no idea who Marc Anthony is. A musician I think, making what passes for music these days?
Try Prana. Yes, "n". They make a lot of good stuff for ectomorphs and it lasts long enough to justify not qualifying for Kohl's racks.
Also, stock up on the last few jeans that are boot cut. The skinny jean movement makes dudes look like sperm, which is funny when it's your teenage boy, but not so much otherwise.
Marc Anthony makes handbags and stuff that Marc Anthony buys for the woman (women?) in his life.
Also, skiing justifies limited shaving. Gotta protect that skin, although with huge goggles that space between limited ski beard and goggles is at risk of becoming a clown strip of skin damage. I hear they have lasers for that.