Question on Cat Food Buying when switching to better food

So, I'm a college age student who doesn't make much. I definitely want to give Nigella the food she deserves and I'm sure I could swing the better quality food (buying health insurance is another ordeal in itself - I've been quoted around $50 a month which is ridiculous). My problem is: I tried before to switch Nigella, bought a whole 24-pack of cat food which set me back around $40-50 after buying a few cans on their own. The first cans I bought individually she didn't seem to mind but then the mixture of the new/old cat food (I was buying Blue Buffalo and mixing it with her Friskies) apparently didn't appeal to her and I felt like I ended up wasting a lot of money. She begrudgingly began to eat it a bit but only after I had to throw away about half the pack because she refused to.

I guess my question is: how do you buy food when you're switching to a better quality brand? Should I buy individual cans (slightly more expensive per can) and give myself lee-way to test out new brands if this isn't working? Or should I buy 24-packs and tell Nigella to suck it up? 

It really depends on how picky your cat is. When I was switching my very picky eater to better canned foods, I was only buying a few cans of a new brand in different flavors to see if she liked them. Yes, it was definitely a little more expensive per can that way, but guaranteed, if I bought a case of anything, she would refuse it knowing her.  I really empathize with your situation because I did feel bad about throwing a lot of food away, Since then, I've started feeding a stray that comes around, so I save all of Aria's rejects for him.

If you have a tried and true topper that you can put on top of the new food or mix into it that you are very confident will get her to eat it, then I might risk buying a case of something new. It is a risk though.

I think I might suck it up and just buy individual cans for now. It's more expensive but that way, I can maybe switch brands/flavours if I find that she's not feeling a certain canned food. It's slightly frustrating and I don't have any strays around me that I know of (probably for the best, as I would feel like I need to take them in ha!) and pet shelters around here don't really use HQ food so they probably wouldn't accept it anyway.

She's definitely a slow-to-transition cat so I'm not sure how long I should wait before deciding that a brand isn't working for her. She took a few months to get settled into the house when we adopted her, and change is definitely not her forte.