Basically, in normal amber games, you have 100 points to distribute on your character. There is extreme flexibility on what you can buy with those points, from ranks in one of the four main attributes (psyche, endurance, strength, warfare), to powers (design attunement, logrus attunement, trump mastery, sorcery, power words, conjuration), magic items, personal shadows (worlds), allies, etc. Infact, there are so many things you can buy that you are forced to chose a scant few of them.
The rules are very interpretation-based. In the sense that there are no actual rules for battle: it is very descriptive, and while generally, if going for straight sword combat, the character with superior warfare stat wins, with creative use of the environment, or by shifting the combat to a stat where you have supremacy (go for grappling after a feint), you can win.
As for the stats...it is up to you on how much to invest in them. I have no actual experience of amber games, but feel like you have to find that nice balance that leaves you capable of facing opponents, but at the same time doesn't eat up too much points that you can spend on powers. And creative use of powers and magic items counts a lot (but they are additions to combat. the heart of combat is about the 4 stats, and about warfare mostly). Several characters, however, in the second series of amber, are focused on spellcasting (merlin, mandor, jasra), and they can kick ass pretty seriously (especially merlin with the spikard...cheater... and mandor with his steel spheres).
Also, you should know that even one point in those skills sets you far above a general human...you can think of humans as having -25 in each skill, with -10 for the greatest achievers in the world. But those points we distributed are just hypotetical. At the beginning of the game, everybody is a human...a very successful human, or an unsuccessful one, but still human.