Kit bag & Contents
For starters lets talk a bit about what kind of bag you need.
I would suggest getting a collapsable day-bag for casual outings, and a weatherproof full gear kit bag for more serious trips. Protecting your gear is of paramount importance, especially when on a long journey into the middle of nowhere. Larger systems require larger storage compartments, with thicker padding. While this may seem like an obvious point, be very careful buying bags online, and be careful to ensure that any bag fits your needs, and your gear, before purchasing it. Some companies use smaller cameras to model their bags in order to make the bags appear larger by comparison. Check the measurrements or google image search 'BAG NAME' along with words like 'full' or 'gear' for peace of mind.
I use currently use a ProTactic 450 AW as my bag, as it is heavily mod-able, and can be tailored for each outing.
With more casual bags, especially ones you will use on city trips or around population centres, they should have very little to mark them out as camera bags by preference. Some camera thieves are really very good at spotting the big brands, and as such are attracted to clear logos etc. Most labels are removable, or at the very least easy to cover up.
Again, this falls into the area of protection. I suggest that you invest, early on, in the three main camera care gadgets. Firstly, buy a blower. While I know that they may look like something from a blue movie, blowers are very important. This is for two main reasons. Firstly they blow air that hasn't been in your lungs (moisture risk), and secondly they can be used with precision (without spitting into your camera). Honestly, I know it may seem a bit OTT, but I cannot recommend one enough to ensure your gear stays in good condition. Number two is a Lenspen. If you don't know what one is, google it. A really very useful gadget. Wash the brush regularly with warm soap and leave to dry. Thirdly, or lastly, is a microfibre cloth/shemagh. These are useful to clear/protect from dust and also aid in cushioning your gear from bumps, knocks and bashes.
I have to confess I don't really use a tripod. I own five, but they don't really match my shooting style, and I don't really like carrying them around considering how little I want to use one. Having said that, in certain situations you won't be able to be without one. Night photography and long exposures are the most obvious examples. Recently, however I have also learnt of clever ways of photographing busy tourist areas. With a tripod, you can take multiple pictures, then combine them in photoshop and remove all the people (it works by automatically comparing the pictures and removing the differences!). Carbon fibre is becoming more and more affordable, so if you can make the extra financial leap- do so. This is advice from someone who once upon a time did not- and regretted it. Alternatively, get a cheap pocket tripod to shove in the outside pocket and just tailor your photo ops accordingly.
Bulb release / Remote Trigger
Yes. If you think you will make good use of a tripod buy one of these. That's it.
Here is a random list of other stuff. Emergency rainproof poncho never hurt anyone, and they come in neat little lightweight packs. Spare chargers (buy a cheap third party one off Amazon). Ditto batteries. I dig spare batteries. Always have them to hand. Paracord - just for rigging tripods, long exposures, also useful for keeping your gear off the ground and out of the wet. Clear ID somewhere in your bag's main pocket. Stitch in a label or just write in it with a Sharpie. It sounds silly but believe me you'll wish you had if the worst happens. Beanbags are good for telephoto stability in cars/safari jeeps etc. If you are travelling to far flung places you can just take an empty bag and 'bean it up' at the other end. Ziplock bags filled with sand, grain or actual beans work well - or even a travel pillow will do in a pinch. Finally: maybe a tiny energy/cereal bar in a side pocket or at the bottom, just in case... you know.
Safe travels, H.