I have been colouring my hair both at the salon and on my own for 2 years because of premature gray hair.
I find all the brands pretty much the same in terms of effectiveness. However, the things I would recommend for you are the following:
Make sure your hair is bone dry. I.e. don't take a shower immediately before. I did that once and the colour was dripping all over the place. What a mess...
Most of the kits come with the basic 2 ingredients you have to mix in a bottle that it comes with, a pair of gloves, and some hair conditioner.
For this type of kit, you basically apply colour from the squeeze bottle and it gets messy really fast. So make sure you do not wear any of your pretty clothing because once the colour lands on it, it is over for it. Also your towels will be ruined. And be careful of where you apply it, because while you're busy tousling your hair with the colouring from the bottle, it is bound to splatter onto nearby surfaces like the walls. So you will want to be in a place that you can easily clean, i.e. bathtub with porcelain tiles. If you do splatter on the wall, clean it up quickly if you can. The same applies to when you're rinsing the colour from your hair. Do not use the shower because you're asking for splatter galore, instead, dunk your head under the tap nozzle in the bath tub and gently rinse the majority of it away.
Now a tip for when you're applying colour to your hair. You mentioned you wanted to go for full hair colour, so I would imagine you would be applying the colour liberally all over your hair, this will cause you to smear colour over many parts of your skin like the ears, the sides of your head, the back of your neck, etc. Also if you have long hair, it will come in contact with your skin. This of course will stain the skin. The stain will not last, it goes away in a day or two, but for a while you will have some coloured skin. I tend to have black ears for a day.
Another thing I have found with hair colouring that lightens my hair is that after application it is dark, and strangely over time it becomes lighter and lighter. Not sure why. So I have started to pick darker colours.
And finally just as an FYI, there are self highlighting kits out there as well that has quite an assortment of things. It comes with the mixing ingredients, a plastic bowl, a shower cap with holes, a special brush, and a pair of gloves. If you're feeling adventurous you can try some self highlights by just applying the highlights to streaks of hair. I never did much with my kit, I just wanted bangs that were lighter in shade.
Finally, get a shampoo that protects your hair colouring.
Have fun! There's nothing to it, just a bit messy at first, you will get savvy after the first time.