Attributes like dexterity and perception are not always 'visible'. You cannot tell ow well someones eyes work simply by looking at them, nor how well they would use a tool based upon how there hands look. You are on the right track with using visible representations to display the characters lack of coordination, but you do not need to be completely literal. The degree of subtly you decide to use in this case is up to you, play around with it. Your description can always be changed later.
The same can be said about ones "aura' it does not need to be readily visible but rather it's a form of 'presence'. Someone with a commanding 'aura' is someone who others are inspired to follow, for example. While Illarion mentions essences as a semi tangible thing, essence isn't something you must immediately link to visible aura around your character. As you can't really force another player to acknowledge seeing a colored aura around your character i would advise against using this sort of visual. you may find that you do not get a reaction, or you may find that the reaction you get is not what you would expect. Illarion has many magical folk, but most don't go around glowing unless they plan to cause trouble. If you choose to use such exotic sorts of visuals then you may want to give it an in-depth background. try to avoid contestable statements like "He glows because he is so powerful." as your new character obviously will not be as powerful as the others around him. perhaps this aura is visible 'only to those who have a sense for magic' or perhaps he has some unrestrained latent talent that tends to peek out when he isn't paying attention.
The best advise I can give is to try and be creative with your character background and description, but try to avoid 'just because' sort of reasoning's as Illarion is a world with it's own set of rules. Try things out, and if they don't work out then change the background of description as you like until you find something that works. Though if your character has alot of friends be ready to have an excuse for such changes
Good luck and have fun, welcome to illarion