Need some tips on how to increase overall temperatures in my terrarium

[Homebody]

Here's my question: substrate temperature in the warm zone is okay, around 31-33 C (88-92F) and my snake likes to sit in the coconut hide, but apart from that, ambient temperatures are almost identical and similar to my room temperature, which is, I believe, a bit too low, around 24-25 C (75-77F). How could I increase the temperature to get a good temperature gradient?

I agree that your ambient is low and that you should raise it to 80F. I caution you to do so carefully, because temperatures that are too high are more dangerous than temperatures that are too low.

I haven't used either a CHE or DHP, but, from the infomercial above, it seems the DHP would be more beneficial for basking species than for a ball python.