BED
First, get a comfortable bed. Get a brand new mattress. They last only about ten years before they start to wear from the inside out. Put a zippered cover on it to prevent it from getting dust mites.

DOG BED
Get Wonder Dog his/her own new comfortable place - look at L.L. Bean for ideas for dog beds. It is important that the bed have only his scent on it. (I learned the hard way never to buy used textiles for pets. I could never get the urine smell out. Even with bleach and sunshine.)

CHAIRS
Second, get one comfortable chair for you and one for your spouse. I might be tempted to get the chairs new, too.
TABLES (and nightstands)
Two options. One, let all your friends, relatives, church members, coworkers, and members of your social group know what you are looking for. You would be surprised what nice things are stored in people's garages.
Option two is to look at consignment shops, used furniture stores and thrift shops.

Small tables do NOT have to match. You could paint them the same color, if you like.
Kitchen table or dining table (with or without chairs).
Table to go next to each comfortable chair.

LAMPS
You will need a lamp in the bedroom that can be reached while you are in bed.
You might like table lamps on the tables next to the reading chairs. I prefer a torchiere lamp to bounce light off the ceiling, with an integrated gooseneck reading lamp on the lamp pole.

DOG CRATE and dog obedience lessons. This is as important as anything else on this list for having a good relationship and shared expectations between the three of you in your new family.

Other Houzzers will have different opinions than I do. Take from this what is helpful.

Best wishes.