I have always used a bag, preferably one giving me the choice between carrying it by the handle or carrying it over my shoulder. I've had various bags over the years, but frankly my favorite was the one that was kitted with the Canon film camera I bought in 1995. I used it with the several Canon cameras I used for the next twenty years, and although it is now starting to fray, it would still meet my needs if I wouldn't feel odd carrying a Pentax system in a Canon bag. Normally I use it to store the limited Canon equipment I retained when I returned to Pentax in June 2015, but I repacked it this morning to show that it could carry my current kit of a K-30, Sigma 10-20mm lens, and Pentax-DA 55-300mm lens. In addition to those compartments, it has a zipped compartment in the lid that I used mostly to hold filters, and a side film compartment that I used to hold batteries during the digital age. The latches which hold the lid closed were reliable as well as quick to operate. In addition, it has a zippered compartment on the back I used to carry a small notebook or any tickets, brochures, etc I picked up along the way.
In the past twenty months I've had trouble finding one of this size and capabilities that is also durable.