Think of one low cost guide to Rome in 48 hours, it was quite difficult. I could be taken for granted on some aspects, but seeing Rome in a weekend is difficult, because it is a city to be savored and understood in every detail, for the magic it transmits.
If I had to think Rome as a tourist (which I would love to do!), I would take a hotel in the Rione Monti, one of my favorites and I would go around the city without taking a single vehicle. From Monti it is in fact easy to reach most places, with a little good will.
For things to see, there is obviously plenty of choice. Being low cost, I would avoid everything for a fee, and would only go on long walks in the most beautiful neighborhoods of Rome.
As soon as I arrive on Friday evening, I would go for a walk in Via dei Fori Imperiali, taking a long tour .. From Monti I would cross Via Cavour, I would go up the stairs that lead to Via delle Sette Sale, passing in front of the church of San Pietro in Vincoli and the Faculty of Engineering of Sapienza (promising myself that I would visit both the next day with the light) on Via Eudossiana, I would go down to Via della Polveriera and wait to find myself in front of the Coliseum illuminated. I would wait some time to enjoy the show, which is magical in the evening, and then I would go down the stairs to get to Via dei Fori Imperiali.
I would go up to Piazza Venezia, stopping to see the holes on the right and left, and then I would go up to the Capitol, to have an even more exciting view of the Forums in the evening, taking advantage of the fountain of the Capitol Hill to freshen up a little (in case it's a nice day!).
On the day I would have a nice breakfast full of life, I would wear comfortable shoes, and I would be ready to visit more of Rome!
From Monti, crossing Via dei Fori Imperiali, I would go towards the Jewish quarter, the ghetto, and I would get lost in the streets, beautiful. It seems to enter another reality. After passing via Arenula you go towards Field of 'Fiori.. For me the alleys of this district are not to be missed .. from Piazza Campo de 'Fiori, Piazza Farnese (where the beautiful Palazzo Farnese is located. The visit is free but you have to book a long time in advance!), Via dei Cappellari, Via dei Banchi Vecchi, wandering a bit through shops, getting lost in time.
Walking you find yourself a Corso Vittorio Emanuele, and in Via della Conciliazione it is really a step ..
Saint Peter arouses my full attention every time I pass by. During the day it is beautiful, but also in the evening it has an unparalleled charm. You could spend hours on the colonnade simply to admire the spectacle. Going towards closing (around 23pm), there are very few people ..
Now to go back, you could take the bus, or .. just pass by Sant'Angelo castel, whose presence has accompanied Rome for almost 2000 years, cross the bridge, head towards Piazza Navona, cut to the Pantheon, come out at Via del Corso, go towards Trevi Fountain, go up to the Quirinale, go down and find yourself in the Rione Monti .. :)
In the evening I would have something to drink at Rione Monti, perhaps at 2Periodico Caffè or Ai tre scalini ..
Finally, on Sunday I would take advantage of it for a tour of the Aventino district, relaxing in the sun at Orange Garden, which offers an exciting view of Rome. A little further on from the lock of the Priory of the Knights of Malta, in Piazza Cavalieri di Malta, you can also see St. Peter's with a very particular perspective .. Before leaving I would visit the churches of the district, savoring a little peace before the departure.