3 Days in Rome - help with itinerary

All the out door sites e.g Spanish steps, Trevi Fountain, The Pantheon, Piazza Navona you should go visit really early in the morning like 7 am to 8 am or really late so you can see them after dark with no tourists. Most tourists go to sites en masse in the late morning to afternoon versus the very early morning and you will not be able to see the Trevi Fountain for example or anything or take pictures without someone with a selfie stick in the way.

Here is a link to other attractions that you may want to go to based on your own interests after a little research
https://www.touropia.com/tourist-attractions-in-rome/ or it is more efficient to consult a guide book and see what fits your interests.

I hope you aren't planning to visit Rome during Easter. Talk about crowds!

There is so much to see in Rome, you have hit the high spots. The Capitoline Museum.

https://www.romeandvaticanpass.com/rome-attractions/Capitoline-Museums.html?aid=140&aid=532&utm_source=bing&utm_medium=cpc&utm_campaign=Non-Brand%20OMNIA%20Card%7CDSA%7CUSA-EST&utm_term=rome-attractions&utm_content=Rome%20Attractions

Also, Trajan's Forum, the Catacombs, Borghese Gallery, Castel St. Angelo and more. Near Trajan's Column there is a church that has the original steps from Jerusalem that Christ walked on.

For your Colosseum tour I would recommend Context Tours. They are a little more expensive but worth the money - great tours and only 6 people per tour. While I agree that late mornings thru early evenings can be very crowded you only have a limited time to see Rome so I suggest going early morning to the sight (s) you most want to see and then see other sights in the afternoons or evenings. As for other things to see I definetely say the Pantheon, Capitoine Hill (their museum is also quite good), and Trajen's and Augustus Forums. Strolling through the Trestavere neighborhood and throught the Jewish Ghetto are quite enjoyable (great restaurants also).

Since you have limited time in Rome, try to group your sights together. Some samples.

Colosseum, Palatine Hill, Roman Forum, Capitoline Hill, Capitoline Museum, Victorio
Emmanuel Monument, Santa Maria Maggiore Church.

Vatican Museum, St. Peter's Basilica, Castel Sant'Angelo, Piazza Novona, Campo de Fiore.

Borghese Galleria, Pinico Terrace, Piazza del Popolo, Spanish Steps, Trevi Fountain, Pantheon.

I would heartily recommend seeing the Pantheon and Trevi Fountain in the evening. So much more interesting at that time. Before dinner during the passeggiata is my preference, but after dinner is great too. Same for Piazza Navona, which will be very lively on the weekend. If you are a small group, I recommend stopping for a glass of wine (and cheese and salumi) at the enoteca Cul de Sac just off the southwest corner of the Piazza.

Getting outside the city to Ostia Antica may be a good Sunday activity to investigate.

Also, April is the height of artichoke season, so be sure to try some carciofi alla giudia (fried/ Jewish style) and carciofi alla romana (braised) while you're there. Particularly if you eat near the Jewish Ghetto.

Thanks everyone!!! Appreciate your responses! Really helpful :)