Your question is a question that's subjective. Meaning the word things?
As in, if the things are small enough to carry multiples of, do they count as one or are each individually separate items?
If you counts these things as individual things, then one person would essentially only carry 3 things, as per your statement.
Example: I plan on taking a gun(is the ammo another thing?) I could in theory, fill my pockets with ammunition, plus have the gun already loaded. I could also want to take bubble gum to chew, so I only get one piece?
However, if I had to choose exactly 3 things - I would choose to take a hunting knife, 200' rope and one quick fire rifle(w ammo. to boot)
Oh there's always one! lol :p you can have a loaded gun... this is one 'thing', you can have one box (or whatever ammunition comes in), this would be 1 'thing', and one full packet of bubble gum, this would also be one 'thing' :-)
My eyeglasses - contacts wouldn't cut it plus, aside from actually being able to see things, I could use them to start a fire, a really big sharp knife, and my husband (lol- even if he didn't want to go). I know - practical but I do want to live
Survival? All is need is my internet access and if I meet a wild creature I will look up a hub on how to deal with it. Oh and I'll read the food hubs on what I will eat after the three months are up - I'll return home skinny of course - you can survive three months without food, but not without water. There needs to be a fresh water supply on this island.