IOW, how sneaky crafty ballsy can you sketch a mortal to make it believable that he will compete on that playing field with immortal royals?
Amberites can walk to/create whatever they desire; granting them all sorts of abilities, but most importantly, reality.
Yes, a Conjurer can create Artifacts that grant them useful abilities; but they can't pay for them, at least not without taking fatal levels of Bad Stuff. 'Reality' is a higher order of initiation, requiring Pattern or Logrus.
But suppose our mortal mage chooses to become
an item desired by an Amberite?
It's tricky, but doable. Creating an item that grants Shape Shift requires the aid of a demon or other shifter, but they are easily paid with enhancements. Rather than setting the desired form, enchant yourself in a Shadow that is Destined to have an Amberite travel to it seeking an item, and let the Patternwalk change the item and creator to the Amberite's desire.
Messengers and modes of transport would be the most common results - Corwin's bird of desire for example. In return for serving the Amberite for a little while, the enchanter gains a permanent, 'real', paid for power! Further, the power is Pattern based, so continues to function in worlds without magic
Although enchanters are the most powerful beings likely to use this trick, quite weak Shadowdwellers could use this - at the risk of forever losing their original form.
Assuming that this trick is used frequently, multiple practitioners are likely to find themselves in conflict, fighting for access to a very limited resource, the handful of Amberites, of whom maybe only 1 or 2 are patternwalking at any time. Victory will likely go to those who own a Shadow whose Destiny they can control.
After a few successes though, these practitioners will likely retire, having acquired the most common abilities - diminishing rewards plus ongoing conflict dissuading them. However, they would know each other, and no longer have a reason to fight - creating a looseknit group with shared history and interests. Possibly these retirees will even take the Unicorn as their symbol, claiming her as the first of their number, created Dworkin's original use of Pattern!