Koop.

Gusset b*****d grips have been great in my experience. Your hands will sweat using any grip yet the rough texture of the gusset grips means that slipping is minimized, particularly in comparison to smoother surfaced grips. Unlike DMR zip grips and other similiar style grips, the gusset bastards are particularly hard wearing so they will not wear down to a smooth (less grippy) surface. As a bonus the b*****d file surface is also great for hardening up your hands against blisters!

There is no particularly strong argument to suggest that as a begginner you should avoid a rear disc brake at all costs. However, if you are intent on running disc brakes make sure they are hydraulic as a good v-brake is often as good as, if not better, than a mechanical disc brake. Also bear in mind that it is almost guranteed that you will want to try maguras at some point, so why not invest in these from the start? It is also unlikely that you will damage a rim brake as you progress, something that is likely to occur if you have disc brakes.

Green rims are fine and for that matter any colour rims are okay. Infact the more individual looking your bike is the better, so many bikes are colour themed in the same way its always good to see something different. However, I'm sure you want to retain some level of good taste in the look of your bike so i would suggest not going over the top with the green and sticking to a maximum of three well balanced colours. Green black and silver for example.

Definetely have a finger covering each brake lever all the time. I suppose if it feels more natural not to cover both levers then do that but its not going to be as safe. There aren't that many occasions when you might not suddenly need the front brake. Furthermore, only using one finger ensures you have a lot of grip on the bar and therefore getting better control of the bike. Make sure your finger is at the end of the brake lever as opposed to the middle or further. By doing this I radically improved my brake performance as a result of having double the leverage. Also a finger at the end of the lever can avoid pinching your middle finger between the brake lever and the bar.

Don't use a protector and you will have even more incentive to make that rail gap and not dent ur shiny new downtube PLUS they look weird and think of all that extra weight

I agree that rocking and backhops are fundamental to learn early on, but in my opinion being able to ride up onto obstacles like benches and ledges etc is equally if not more important. Backhops need to be learnt in order to do more precision moves, and in many cases after you have managed to get onto the object. As a beginner you wont be using backhops to get onto objects plus after all that trackstanding doing even more "flat ground" practice will get a bit tedious! If your set on learning backhops though, try doing a small endo in order to rock onto the back wheel. This means you can focus less on getting into the back hop position and more on what your meant to be doing when your up there. The movement of rocking from the endo onto the back wheel will initially make balancing easier aswell.

Hey, I wouldn't worry too much about what particular make and model of bike you get. I'd say get what is cheap and available and not to bother too much about frame sizes etc. As long as the bike is remotely "trialsy" its going to be okay to start riding on. A lot of people start on their standard non-trials bike and get a long way on that without having to fork out money on a trials specific bike and then realise they're bored of trials. So I say get any low framed hardtail you can and practice loads and then you can get a super expensive steed and be confident that you know exactly what you want from the bike!