I think my Cat is sick, and I don't know what to do :(?

I am 16 years old and I have a Cat, a desert lynx, she is only 2 years old, and she has always been in exceptional condition. Yesterday, I noticed she was sneezing a lot (as in, at least two sneezes every 3-5 minutes), and today the sneezing is continuing, and she seems lethargic and her eyes are kind of runny. She is breathing louder as well. I have never had a sick pet before and I don't know what to do. I gave her water, put her on a soft comfy rug in some sunlight, and handed her a few cat treats. Should I take her to the vet, or wait a little longer (seeing that a trip to the vet's is pricey, If I don't have to go, It would be great, but my cats wellfare comes first). Please help :( Thank you