I am using caltex havoline formula and thats a very decent oil for most type of cars (much better for hot summers as well). Just make sure the person you bought it from wasn't using fully synthetic previously in which case its recommended to continue with same. For filters, I'd suggest you go for genuine toyota (atleast the oil filter). For air filter, I believe local corolla models air filters also fit vitz so you can use that.
Thanx a lot. As u can see I dont know much about Vitz car but its a great ride and am preferring it over my corolla for usual driving in Lahore. I will check from previous owner about the oil. Also, I will try to mix a proportion of high octane as recommended by some here. It doesnt give good mileage within city but gave reasonable one when i drove it to Faisalabad recently.