Contact Yucatreks for a smaller, personalized, van tour.
Most big bus tours from the resorts to anywhere begin at about U$100 per person.

Tulum is a modest set of mostly ruined structures, with one in a very imposing cliffside setting.
Chichen Itza has extensive grounds, big buildings, and lots of vendors and tourists.
Ek Balam has some gorgeous sculpture/carving halfway up a well-restored pyramid you can climb, in a small, beautiful jungle setting, great for dramatic photos.
Coba is mostly partly excavated, but has a less restored pyramid to climb, and an extensive, shady site to see by bicycle or bici-taxi.
There are lots of videos on YouTube that show all of these ruins, so you can get an idea in advance.
We much preferred Ek Balam and Coba.

All the ruins have cenotes nearby, and Tulum has a beach. Combine a ruin and a cenote for a whole day's outing.