You can get a combined ticket to visit the Colosseum, the Forum & the Palantine Hills which is valid for 3 days. If you go to the Palantine Hills site there are hardly any wait for tickets. The Palantine Hills site is a great site to explore with views over Rome, the site links to the Forum which will be much busier, and you can exit directlt opposite the Colosseum. You then bypass the line for tickets which in May last year was about 45 minutes but you will be in the site in just a couple of minutes.