It's easy to find all the tourists sites in Rome. They are pretty close together. Right after walking around Piazza Venezia, we found the Roman Forum. There is a lookout point to the site and you can just walk around it to see the ruins and take photos. It's really beautiful in person and I liked having the vantage point of being high up to take photos.
I didn't see the point of paying for the entrance fee anymore so I just took my time looking at the ruins and snapping photos along the way. You can definitely buy the tickets to the Roman Forum and explore it together with the Colosseum.
It's less crowded than the Colosseum but equally as stunning. And you keep walking around it, you will find the Colosseum in front.