Click upgrades make no sense. EXP is gained after X number of clicks, starting at 10.
There's no "EXP per click". There's no "Click Speed". There's no delay between clicks.
"Idle Earnings" shows earnings despite there being no idle earnings in the game, at least at the start.
It wouldn't surprise me at this point if "Percentage EXP boost" didn't do what it said it does.
These are basic things that are impossible to miss.