You could pass the reading and listening sections of a C2 exam having only paid for LingQ and having studied free material you found on the Internet (particularly YouTube, podcasts, news websites, literature, etc.).
You won’t be able to pass the speaking and writing sections though. For that you need to hire a tutor or find natives to talk to and critique your writing.
From my experience with Italian, I passed the B2 reading and listening sections when I reached the old level of LingQ Intermediate 2.