Polo shirts are really versatile due to the collar, which takes them up a notch on the smartness level compared to the humble t-shirt. For an everyday casual style you can wear your polo shirt unbuttoned with a pair of chinos. Or up the trend stakes and button the polo shirt to the top and wear with a pair of formal tailored trousers.
Keep it looking its best by drying it on a hanger (rather than flat) to preserve the collar shape and avoid tumble drying. During colder months, try out one of the newer long-sleeve styles and you won't be disappointed.