Partial walkthrough, assuming you have explored to find the locations and the relevant items:
High school:
First trip - weapon
Second trip - take the green magazine
Third trip - take the blue serum
Fourth trip - take the purple dildo
Completed. Sending someone on an expedition will have them find clothes
College Campus:
First trip - take a med kit
Second trip - I think you need to take the rifle or pistol which are just white square icons in the inventory at the moment
Third trip - backpack
Fourth trip - Katana
Completes with prize of a stereo system for the shelter
EDIT 17/06/21:
Central Hospital:
First trip - fire extinguisher
Second trip - hand gun (any weapon might work as the success test jus mentioned weapon)
Third trip - dildo or Snow
Fourth trip - weapon
Fifth trip - blue serum
Sixth trip - katana
Success unlocks repeat visits rewarding med kit
Edit: 17/2/22
Shopping Mall:
First trip &until success at darts - dart board
Second trip - katana (any weapon?)
Third trip - newspaper
Fourth trip - porn magazine
Success unlocks fishing which provides alternate food source
Edit: 25/03/22
Research Facility:
First trip - map
Second trip - weapon (I used gun)
Third trip - weapon (I used gun)
Fourth trip - purple syringe
Fifth trip - bolt cutters
Unlocks Amber the futanari
Edit: 15/05/22
Police Station:
First trip - weapon (I used katana)
Second trip - bolt cutters
Third trip - med kit
Fourth trip - weapon
Fifth trip - red syringe
Unlocks Radio
There might be an extra trip here and there I'm not entirely sure but the item sequence is accurate I think
Item guide:
Food and water: Sustains your people, found through exploring, can be traded sometimes in the morning
Wood: Used to reinforce barricade, found via exploring
Green serum: Cures infection in a girl via the "heal self" option
Blue serum: Cures janitor in high school expedition
Red serum: ???
Purple Dildo: Relieves Snow in high school expedition
Backpack: Used in college expedition
Red magazine (porno): ??
Green magazine: Removes plant in high school expedition
Rifle: Used where weapon required
Pistol - Used where weapon required
Med kit: Used to restore health of your people and in college expedition
Old newspaper: ???
Fire extinguisher: Central Hospital
Dart board: Used for recreation and ??? (you can take it on expeditions)
Katana: final stage of college expedition
Polaroid guide:
1. "Scarlet Unwinds" - have Scarlet masturbate
2. "Junpiers Cellphone Gallery" - have Juniper masturbate
3. "Raven loses focus" - have Raven masturbate
4. Not implemented
5. "Snow has fun" - have Snow masturbate
6. "Scarlet caught by zombies" - scarlet gets raped while exploring
7. missed the name of this one - Juniper gets raped while exploring
8. "Raven meets zombies" - Raven gets raped while exploring
9. Not yet implemented
10. "Snow creampie" - Snow gets raped while exploring
11. "High school rescue" - rescue Snow from the high school
12. "Research assistant rescue" ???
13. "Raiders scarlet target" - raiders rape Scarlet (random possibility during time skip with no barricade)
13. "They cum for Juniper" - ???
14. Not implemented
15. Not implemented
16. Not implemented
17. " Red + Green" - Have Scarlet and Juniper masturbate at the same time with high enough relationship (hearts on character screens)
18. "Red + Purple" - Have scarlet and Raven masturbate at the same time with high enough relationship (hearts on character screens)
19. " Green + Purple" Have Juniper and Raven masturbate at the same time with high enough relationship (hearts on character screens)