I have a better opinion if you want to figure out if you have strep throat or not. Hopefully, it's just a sore throat or flu, or cold.
Super cheapest method: May be unreliable, but if you really have it, you will see it, and you don't even have to spend over a buck if you have to buy these.
If you really want to see if you have a strep throat cost effectively using home stuff.. all you need is 3 things:
1 - a petri dish (the little clear plastic containers)
2 - a long cotton swab
3 - someone to help swab the back of your mouth with the swab, make sure you get a good decent swab all around so you don't miss it - maybe your have BF do it or something.
You then swab it onto the petri dish, close it up, don't open it for a few days and if you start seeing weird bacterial stuff growing on the bottom, you got the cheapest confirmation that you have strep throat.
There's other OTC stuff you can go check out at your local pharmacy, I think they're like strep throat tester plastic things that cost like $20-30 for a pack of 20+ish. It costs some money, but it can get the job done in like 15-20min.
These are two very cost effective methods that will save you the trip to a clinic if you don't have strep throat. But if you do have it, you should go talk to your doc immediately.