Wear a navy varsity jacket with blue chinos for a simple ensemble that's also well put together. To give your overall look a more polished aesthetic, complete your look with black leather loafers. Ensembles like this have a refined air that befit men in their thirties very well.
If you'd like take your casual game to a new height, wear a navy varsity jacket and blue chinos. Let your sartorial expertise really shine by finishing off your outfit with a pair of black leather chelsea boots. As you pass the big three-oh, you probably want to start dressing maturely. If that's the case, ensembles like this are ideal as inspiration.