Dog first aid kit?

We have just rescued a shelter dog from kill shelter...sweet thing too.

What do you all carry for first aid for pup? We are going to desert south west with
her shortly...so tweezers and pliers for cactus... What else do you bring just for dog.
Benadryl I have in children's dosage.

ANY ideas on how to introduce her to cactus...as in ny, we don't have any...except for the hard way.

Mali thanks you.