gear

I decided to buy some gear.

"Gear" is equipment or accessories that you need to do something in particular.  Notice the following:

1. Are you bringing rain gear with you?
   
2. I want to look at the camping gear.
   

traverse

A good map of the area I was going to traverse.

To "traverse" a place is to pass or travel though it.  Notice the following:

1. It was a very long walk traversing the desert.
   
2. There are people that traverse this land every day just to buy milk or sugar at the store.
   

not prepared

I was not prepared for how difficult it was going to be.

If you are "not prepared" for something you are "not ready" for it.  It is possible to be not prepared mentally or physically.  Notice the following:

1. We weren't prepared for it to be so sunny here.
   
2. He was not prepared for all of the work he would have to do in university.
   

or else

Drink lots of water or else you'll get dehydrated.

In this sentence we can omit "or else" and just say "or you will get dehydrated."  We add "or else" when we want to emphasize that there is a cause and effect between the two situations.  Notice the following:

1. You have to do all of your work on time or else you will fail.
   
2. She needs to exercise more or else she will get fat.
   

elderly

I met lots of nice hikers, especially elderly hikers.

"Elderly" is a nice word for old people.  Notice the following:

1. He volunteers with the elderly community members.
   
2. After my grandfather died, my grandmother moved to a home for the elderly.