Principally, the route is accessible all year around, but especially in winter it is not recommended at all for inexperienced hikers. Even in summer, there may be temperatures close to the freezing mark at night, in winter temperatures drop to -40° degrees celsius.
Speaking of supplies: On the route, there are possibilites to buy some food at the mountain stations, but even for swedish norms they are fairly expensive. You better bring along cooking equipment and food. You can use the water of the many small alpine brooks without hesitation. Moreover, you should pack a small first aid kit, enough insect repellent and a map.
Since it is a long-distance tour over several days which ends about 80 km southern of the starting point, ist does not make too much sense to use Your own car, from Gällivare You better take the bus.