So start with a quick sweep for functional-looking knives, followed by pieces of armor that look like they'd cover your skull or torso without falling off. No point to armor if it fails to protect you, or hampers your movements enough that you'll be taking more hits from lost capacity to dodge than the armor can soak up.

If the walls don't seem to have closed in much by the time you've got all that located and equipped, think about the junk you've already searched through. Optimistically, you may by this time have located several instances of the same model of gun with only one core problem each, in which case grab all of them and swap parts around (being careful not to drop otherwise good parts into the mud) until you've got at least one functional gun. Or, you may not have found anything that looks remotely like it could be converted into a useful approximation of a gun in the time available, in which case forget it and gather up whatever else you think could justify the effort of carrying it on your back.

Extending the metaphor, load-bearing gear is anything that lets you carry more of everything else with less discomfort. By it's very nature, that kind of thing needs to be fitted individually for best results, so don't just settle for a backpack or 'supportive community' that looks nice at arm's length but aggravates your spine when you actually try it on, especially if it isn't adjustable. If you've only found one or two useful items anyway, don't even bother.

Medical supplies would be investments in maintaining your literal health as well as non-crisis-averting skills and resources, so you're less likely to burn yourself out if one of those problems gets a grazing hit in. You should be especially careful to make sure that medical supplies you're picking out of the garbage aren't contaminated somehow.

Finally, a grenade would be any sort of clever political stratagem which could avert a range of related bad ends without much further work on your part, or else blow up in your face.