The cartoon series La Brousse en Folie and Le Sentier Des Hommes by Bernard Berger will give you an insight in the local culture and tradition. The comics are written in French, the former imitating the local accent and grammar or lack thereof
Other than that, plenty of conventional souvenirs shops may be found throughout Noumea.
New Caledonia is expensive compared to Asian countries but, like everywhere else, cheap compared to Australia. Much of the food needs to be imported. There is no culture of bargaining either and attempting such might cause offence.A beer in the super market is 150CFP. In some of the camping areas meals can be acquired for 850CFP. Restaurant dining can be comparable prices to Australia at around 2200CFP for a main dish.