Similarly I like to get very cheap ($40-$70) round trip flights to random town and explore around. Unfortunately my uber from the airport to the town is usually more expensive than the flight. Most small towns don't have much in the way of airport buses.
Out of Denver, and I use the date grid on google flights. Frontier and spirit fly to Miami pretty consistently for a $80 round trip, but most flights are to like bentonville, AR or similarly random places.
The key is to people able to take a flight at any time and day, so you can always take the cheapest options. But also if you book 2 months in advance you can go anywhere in the Caribbean/central America on spirit for $100 or so.
