So civilisation has collapsed. Just because people are becoming animals, there is no reason to go naked. Let's talk about what the decerning survivor will be wearing. Let's talk comfort, warmth, laundry and colour.
This article is inspired by The City Girl's Guide to Surviving the Apocalypse. It's full of practical advice and @arbitrarykitten's writing has accessible style. I asked if she'd mind if I wrote this article and she agreed.
(Image credit: Max Pixel Creative Commons CC0. Image recommended by @mikeill)
Comfort
Get comfortable clothes. Except for the base layer, your clothing should be loose fitting. You need the maximum range of body movement possible. Your tactical parkour skills might impress a marauding gang enough that they give up on the chase. Don't wear anything itchy since you'll be in these clothes for days.
Warmth
Clothing is your first shelter. Multiple loose lighter layers are better than single heavier garments. Have a wind-proof and water proof layer. Many of the city-dweller / sporty rain gear will only keep water out for a couple of hours. A garbage bag will keep rain out for longer.
Air your clothes every couple of days to evaporate the moisture that builds up in the layers.
Get a good base layer that will wick sweat away from your skin and keep you warm if wet. Better yet, have two base layers so you can wash-one-wear-one or wear-both.
Laundry
Yes, I did say wash: clothing's performance drops as it gets dirty and a smelly human will be a dead giveaway. Sweat left in clothes will rot the clothes faster. Don't use too much soap because that clean smell will give you away. If you can't find low-scent soap, then use a little baking soda.
Flapping laundry is a flag that marks your position. Hang clothing along a secluded alley that funnels a breeze. Or hang on a pre-apocalyptic clothes line in an enclosed yard. Wet clothes hanging on a line right after rain doesn't look unusual if done correctly.
Look for a place that gets good sun, but isn't visible from the surrounding buildings. Find sun-warmed rock piles or rubble and place your clothes out. You don't want your drying clothes to contrast against the background so avoid drying on large flat concrete slabs unless they're in enclosed yards.
Colour
This isn't Mardi-Gras. Go with muted tones so that you're harder to spot. Greys work well in urban areas. Darker greys aren't terrible in wooded areas if you stay in shadows and low to the ground.
Large blocks of bright colours are the worst. Leave the fluoros, reds, yellows and oranges to the emergency services.
Military chic might be in right now, but avoid looking too tacti-cool because that marks you as somebody who might have a base camp worth raiding. The secret of camo is to trick the eye into skipping over you. Grey will do that just fine, and you won't look out of place when you are spotted.
I sincerely hope we never find this information useful. The two weird items are: garbage bags and baking soda. Both of these have many uses so are totally worth scavenging. Let me know your thoughts in the comments.