One of the cheapest and easiest ways to get from Cancun to Chichen Itza is by joining a group tour with other travelers, which you can book online or arrange with your Cancun hotel when you arrive in Mexico.
Chichen Itza tours are very popular, so there are many companies offering them every day of the week. You’ll be picked up from your hotel in the morning, driven by van or bus to Chichen Itza, and then given a guided tour of the ruins.
We used one of these tours ourselves and had a great experience. There are even early morning tours where you can beat the crowds and be one of the first people to enter the Chichen Itza ruins at the start of the day.
Oftentimes these group tours from Cancun to Chichen Itza also include other great sights of the Yucatan peninsula, like the Coba ruins, Tulum, Valladolid, and a swim at one or two of the many scenic cenotes in the area. These tours usually include a buffet lunch and hotel pickup / drop-off as well.
The only downside of a group tour is that you have a fixed itinerary, so you usually only get to spend about an hour or less in each location you visit on the tour. Personally, we could have stayed a bit longer, but for most people this is probably plenty of time. We tend to take a lot of photos.