Hi Pumpkin82.
How cheap is your "cheap"? good food at reasonable prices can easily get them at any food court in the malls. for family restaurants, try Ponderosa, pay any main course and get buffet spread (49Qr) on the house, eat till you drop. If the local coffeshops or cafeteria, can try Ananas or HotChicken outlets. I've no regrets in these 2 locals establishment so far. Or else, you can try in Al-Nasr near to Doha Clinic Hospital area. There is a long stretch of street with food outlets which you can try on. Ranges from Filipino, Turkish, Thais, Indian, Best Fishes (must try), KFC, McD, Chillis, BK.