Best of luck for ur purchase.
Afa mileage is concerned manual gives 14kmpl in city with normal foot and without ac.
Rest u can have an idea, I.e. with ac mileage will reduce, on highway it will improve (17 to 18 without ac).
On cng standard 50 ltr tank with 7kg gas yields avg 120 with ac, without ac its around 130 with lite foot.
These are usual figures as u required. Btw mine 2006 gives abt 17kmpl in city without ac. Also has v good mileage on cng, but I have removed cylinder in november. Enjoying petrol now....