For all my new readers, here’s my quick take on those items:

• Lens caps are not needed except when a lens is packed away. They are great picture-preventers. Amateur shooters always nervously replace their lens caps after every shot; pros never use them. ‘Nuff said?
• Lens hoods: definitely, and always. Indoors, outdoors, day, night. The lens hood protects from damaga, sticky fingers, and flare. Do make sure it is the right hood for the lens you are using, and do make sure it is on fully, until the click (else, vignetted corners will result).
• Filters: nope. Except when it is snowing, raining, etc. As you know if you are a frequent reader here, filters can give you more flare. They are only needed if the lens could otherwise get dirty, wet, etc.
• Camera bag: Nope. A picture preventer also. A lens and accessory bag, sure, but the camera is better off not hidden in a bag.

So. All these are useful items to own, but you should use them judiciously. Which often means, “not now”.