What Objects And Tools My Dog Needs?

A bowl and toys. Bed is optional, they'll just as likely sleep on the floor or the couch. If you want, you can buy a pet toybox, just be prepared for your sims to constantly want to put the dog's toys away. Also you don't actually have to get the dog agility stuff, that's also in Pupperstone Park.

@TresaofPern @Kalaksed my Sim has two pets a cat and a dog. can my Sim just buy an automatic feeder so they can just share on it? does the toys and objects my Cat enjoys also does my dog enjoys?

You can get an automatic feeder, it's very convenient, but you'll have to refill it though from time to time, more often with two pets eating from it. If you get a toy box both cats and dogs can take toys from it I think.
With a dog you need a food bowl or automatic feeder, some toys, and you need a bathtub too so when your dog gets dirty and stinks you can give it a bath (if you don't have one in your house already).

@kalaksed puppies and kittens doesn't do naughty things like adult cats and dogs do?