Sassy is in kidney failure. Get a copy of the lab results and you can join email lists, very helpful. Dogaware.com has terrific advice as well. The email lists are posted there I believe.
I forced the vet to give Sassy subcutaneous fluids, he didn't want to to it. She is chronically dehydrated as she hates drinking water. I think dehydration makes her feel as bad as the poisoning from the wastes she has trouble excreting. On the SubQ she has rebounded. If your vet says do it, DO IT! It isn't hard or dangerous but it is nervewracking sticking a needle in your pet and keeping her still for 15-20 minutes [for 500 ml, you would give less]. I am spending a lot on the stuff but Costco sells a carton of 12 one liter fluid bags for $25 or so. The tubing cost more and the needles are practically free. You need a prescription for the tubing and fluids. Spendthrift me spends about $5 for one 1000 ml bag of fluids from the pharmacy, $3 for a tubing set and maybe $.10 a needle both bought online. That lasts me a week but I would like to add in another liter bag of solution a week, she just does so well when she gets those fluids and more often the better. I warm the bag and run fluid through the tubing so there isn't any cold shock. The needle is easy to insert and really doesn't bother Sassy much. Have the vet tech show you and maybe go back for more than one lesson if you aren't comfortable doing it yourself.
The diet, see dogaware for information. If cooking is too much for you right now then use canned, not the nasty corn pop kibbles if you can possibly afford it. Or maybe buy a couple of cans to use as gravy for the kibble. Water plus that kibble - yuck. I prefer to make up stuff that looks like canned dog food rather than the bits and pieces Mary Straus feeds her dog but the idea is the same. I plan for 11-14 mg of phosphorus per pound of dog and 20 calories per pound of dog and at least 1 gram of meat protein per pound of dog. I was cooking the food into a mush and watering it down to feed it but her highness prefers a deep plate with meat, rice and pumpkin custard these days. I top it off with warm water still, she just will not drink water! The main addition is calcium. Add 1/2 tsp of powdered egg shell per pound of meat fed. The K9KidneyDiet group has a spreadsheet that will do all this work for you.
The only medicine Sassy needs so far is Pepcid for an acid stomach. She stopped eating last August and that stuff worked wonders. If phosphorus is high in the blood test then a phosphorus binder is used, Sassy hasn't needed that yet. There is a probiotic specifically developed for kidney diseased pets but I am using an OTC product. There are other ulcer medications that could be needed and drugs for anemia but so far so good here.
If treated kidney disease often just lays in the background and dogs live just fine for years with the 25% kidney function they have when it is discovered. I know Sassy is better off today than she was back when it was discovered. Not just more alert and feeling better - she lives for the delicious gourmet real food she gets these days.