Much has been written about photographic equipment and all I want to do here is give a few thoughts based on my own experience.
It is worth bearing the following points in mind:-
Before purchasing any equipment you need to be clear what kind of photography interests you. This may determine the choices available to you. For example some cameras are designed for fast autofocus and some are designed for a slower approach.
Tripod - a good steady tripod is possibly the best investment you can make. Personally I favour one without a centre column. A centre column adds weight and reduces stability. Having no centre column allows me to get close to the ground, and some of my favourite images are taken only inches from the ground. The tripod and head combination should be sufficient to hold steady your choice of camera and lens.
Head - When using a tripod you need to also use a "head". This screws onto the top of the tripod and you then fit the camera onto the head. A decent tripod and head should allow you to easily position the camera and keep it steady. Currently I favour the Arca Swiss P0 head. It is lightweight and holds things rock solid. It has stops at both ends to prevent the camera sliding off. It can be levelled even if the tripod is not level and it can be used for basic panoramas.
Cable Release - there are numerous types on the market. The important thing is to use one to avoid camera movement.
Camera Bags - The problem with camera bags is that they used to be good at holding your photographic equipment but useless at also holding your spare clothing, food and other essentials. However nowadays there are some excellent bags available from companies such as Lowepro, Shimoda and F-Stop.
To carry a long lens I prefer to use a mountaineering rucksack and protect it with a piece of closed cell sleeping mat cut to size, with the addition of a circular shaped piece at the bottom of the rucksack.
A tripod may need a heavy head to manage a long lens, especially if using a gimbal type head which allows greater freedom of movement. However the weight can be prohibitive so I will sometimes just carry an empty bean bag. This can then be filled with some grit when you arrive at a location.