To go out during the night and to do things was dangerous. There was no rule about anything and you did not know what to expect.We needed to go out to get things.Gangs and complete absence of any law was problem.
Constant shelling and snipers from enemy army was minor problem comparing to gangs. I think every city have criminals, people who live on edge of law,murderers, drug dealers and that kind of people.
In SHTF worst kind of people are mostly in charge, they formed very fast some kind of their own private army, in some cases their number was in hundreds, they were drunk from feeling of endless power, because of them you needed to be uninteresting, small, invisible.
They had everything, food, guns, luxuries, they owned black market. If they wanted something from you, eventually they get that from you, your food, house, wife, does not matter what. Only chance for you was that they did not notice you, or your other chance was that they see you have enough men and firepower so that what they want is going to cost them too much.
If you expecting some kind of fair fight or honor in SHTF, forget it right now. We just stay away from them, there was not Superman or Batman in city who saved good people from bad, if we met them it was shoot and run.Most of that folks did not vanished after SHTF ended, most of them still alive, some of them trough that power still have power today, some in private companies, some in politics.
Anyway to go out you needed to prepare some things, rifle,pistol,ammo,backpack,dark clothes, boots or shoes-kind of boots good for running, good for walk on broken stuff and trough ruins ( kind like adidas sport shoes ) in backpack i usually had more ammo, food for a day, candle or lamp, water for a day,sometimes some tool, key was to have some things in case that you need to stay somewhere hidden for a day, outside your house, but in the same time you needed to stay very light and mobile and not to attract anyone. So to had big backpack full of good thins during that trips(even if i had good things) was not good idea.
We took that trips never alone, always 2-3 men. About clothes, no specific rules, as long as it stay in dark color and does not catch too much attention, i used old overall (German army-something similar to US flight suit) and jacket similar to American jacket from Vietnam war. It did not looked fancy, but it worked. Small axe was nice thing to have , for fight and as a tool.
Some folks used small military shovel (folding) with sharpened edge, again as a weapon and as a tool. Every trip was mix of scouting and running,for example if you needed to cross over open space, like street first we spent some time checking for possible problems.If you seen other group of people, always hide until find out who they are and what they want. In short it was always like moving on enemy ground.
To add more about gangs: Yes they even had their own prisons, houses for fun, sometimes they abducted people for ransom, sometimes just for fun, there was no rule.