For the average Amberite attempting to record most forms of skills and talents are irrelevant. An Amberite has the ability they need to find the best places to learn, manipulate events so they can get the training, and the time to study anything in as much depth as they could want. For any typical mundane skill, it can be assumed that the Amberite is easily the equal of any normal human on earth competent in that field. Driving, flying, playing chess, chemistry, medicine, law, writing, investigation, reasearch, history, whatever the subject is, they're good enough to be an expert by most standards. However, there are some areas where it's useful and relevant to note the skills of a character.
The first instance is extraordinaray skills. While most characters can be assumed to be the equivilent of human experts, with superior genetics, hundreds of years and infinite shadows filled with ininite instructors, an Amberite can very easily surpass the levels of skill mere mortals are confined to, especially if they put their mind to it. Putting points into a skill like this indicates an enormous competence in the field. An Amberite with a Knack in Chess could pounce several grandmasters simultaneously. With a Mastery in Chess, they could play every grandmaster that ever lived, at once, blindfolded, with a two piece handicap.
The other talents that are typically recorded are those that a normal mundane human would simply have no access to. The skills involved in sorcery, using the Pattern to walk through Shadows, or draw trump cards are examples of these. Asides from Powers, knowledges related cosmos-scale subjects, like locations of particular Shadows with interesting properties, how to properly identify and greet a visiting Chaos Lord, design a trump-based computer, or remembering the complete in depth history of the Royal family of Amber and major dignitaries from nearby Golden Circle Shadows are also canidates for this sort of talent.
In either case, there are three levels of talent, Knacks, Expertise, and Mastery. The greater the level, the more time and effort invested in learning it, and the greater your depth of knowledge and ability in that talent. Since there's no particular list of skills to choose from except the player's imagination, there're two further caveats: first, the more focussed the talent, the more effective it is, and second, talents don't stack. If two people face off with rapiers, the one with a Knack for Swordplay will beat the one with Knack for Combat, if they're equal in all other respects. And someone with a specific Knack for Rapiers would beat other, in the same conditions. However, if all three are disarmed, the one with the Knack for Combat is suddenly in better shape than the two with more specific Knacks. It can pay off in the long run to have both specific and broad talents so that you can handle the general situation but also have an advantage when the circumstances are in your favor.
For most Powers, the first step is to undergo the appropriate initiation rites for the usage of the powers. Walk the Pattern, traverse the Logrus, unlock the potential of shapeshifting, learn the fundamental mystic arts or the secret of making Trump.
Powers are divided into two types, Major and Minor, with the difference being the degree of power and universality of the power. In terms of Power, a Major power will almost always beat a Minor power, unless the user of the Minor Power is overwhelmingly superior in skill in comparison to the Major power user. Between Major powers and between Minor powers, the difference in power is small enough that skill determines the victor of a contest more than any intrinsic aspect of the power itself. In most games, Pattern and Logrus will be the only Major Powers, while Minor Powers will include Magic, Shapeshifting, and Trump. However, some games may raise or lower a power in strength, such as making Trump a Major Power, adding particular powers like Abyss or Elemental Mastery, or removing powers for various reasons. Addditionally the players may have the option of creating their own powers for their characters, working with the GM, and in some games it may be sufficient to simply say something like "I'm taking Mirrowalking as a Minor Power" and explaining what this allows you to do.
A Major Power costs 10 points to become initiated. A Minor Power costs 5 points for the initiation.
In general, the mere act of intiation does not give the user the knowledge to efficiently and correctly use his new abilities, mere the potential to do so. Having just walked the Pattern, for example, a son or daughter of Amber still needs to be taught how to walk across the veils of Shadows, how to manipulate the environment with a thought, and so forth.
Skills for the utilization of powers are purchased much like any other skills. As with other skills, the narrower the skill and the more invested in it, the more facile and powerful you are in using that aspect of the power.