Very ill cat....need help!

Cat adopted from a shelter, told she was 1 year old. Took her to a vet as she hasn't been eating well for 2 weeks. Vet said she is likely 16 years old ! and not well at all. 

Blood work revealed 16 abnomalities: Some include

non-regenerative anemia

low albumin ( blood protein)

elevated bilirubin levels

imbalanced electrolytes

elevated prancreatic value called Amylase

Vet is thinking possibly viral infection like leukemia, blood infection(mycoplasma) or pancreatitis.

Naturally more blood tests and work needs to be done but vet bills are huge and costly and hard trying to figure out what is wrong with our beautiful cat. Anyone experienced any of these? Because money is tight, which tests should be done first? 

She is not vomitting/diarrhea...... She is drinking more water than usual but eating only 5 little pieces of cat kibble so she has lost lots and lots of weight.  She acts unwell, depressed and hides sometimes. We think she is nausea as she is scraps near her food dish but doesn't eat. 

Heartbroken and incredibly worried.......... only had her for 5 months and so worried we won't have her for much longer.

I don't know which tests should be done first, but maybe if you explain to the vet that money is tight they can advise you which things are most important to have done.

I personally would want to focus on things that can make the cat feel better right away, more than finding out exactly what may be wrong. Ask your vet if anti-nausea medicine would be a good idea, and maybe an appetite stimulant so she'll eat? Is she dehydrated at all? If so, sub-q fluids can be given by the vet and will usually make a cat feel better quickly.

I would also offer different kinds of food, including wet cat food, baby food meat, treats, etc. Really yummy things to tempt her appetite.