Sorry to hear about your not very fun experience with the game! There is probably not enough instructions in the beginning of the game, I will improve this in an update (which will come out next week at the earliest though, since updates are currently blocked because this game is still being rated as part of the Kenney game jam).
If you'd like to give it another try now already, here's how to progress: You have to stand close to the tombstone and press the interact button. Then after purchasing the first upgrade, something new will reveal itself and you have to reveal it fully.
And after that it's pretty much more of that, exploration and upgrades :)