There is one place that is truly cheap in Rome and that is the "Camping Village Roma" OR "Plus Camping Roma"... different name, same place - they just haven't quite decided on a name yet. This is one of the only two campsites within Rome. I would define it as a bungalow plantation, as there are more than 1000 of them, but the atmosphere at the restaurant and bar is good. The modern and tiny bungalows have air conditioning and there is everything you could possibly need. You will meet a lot of nice travellers here. It's the closest and cheapest accommodation in Rome, starting at only 8 Euro per night and it's at about 20 minutes bus ride from the center - 10 minutes on a bike. Book early online for a better price; I've used it once and got 6 Euro per night! For some incomprehensible reason they have two websites (one for each name) here they are:

Camping Camping Village Roma - Roma - Lazio - Italy - Elite Club Vacanze
PLUS Camping Roma | PLUS Hostels

The address is Via Aurelia, 831, 00165 Rome, Italy. If you can't book it online, just crash it... chances are they will have a place for you as they have more than 1000 beds available. Because of this, it's not my first choice, but if it's cheap you're after then that's the place for you.

If you are looking for a more peaceful place on the hills in the countryside North of Rome (about 20 minutes riding distance) and with charm, this is a better option:

The Seven Hills Village Camping
Seven Hills Village | Camping in Rome

It is also a bit fresher than Rome during a hot summer. I haven't visited this campsite, but it looks like it has charm. It is located in a nice place in the countryside, at about 10 Km from the center, but it’s well connected. A peaceful place to rest and a good base point if you are on a bike.

The only other campsite in Rome is the Camping Flaminio, which I also have not visited:

Camping Flaminio - Camping Roma

Have fun in my city and remember not to pay seven Euro for a can of Coke around San Pietro!! The most you should pay for a can of coke at a bar is two Euro. Keep in mind that if you sit down outside a cafe you will be changed twice as much. This is normal.