What things are important here?

Hint 1 of 5:

First, it's important to read about every item, and know what they are used
for.

Hint 2 of 5:

Second, discover what items are still available, and purchase as many as you
can afford.

Hint 3 of 5:

You can always re-visit General Outfitters when you need something else, or
after you have more money.

Hint 4 of 5:

There is one other item located here... inside the Vacant dressing room.

Hint 5 of 5:

Note the message on the wall as you are about the leave the dressing room;
it's another four-digit number.