Doctor Faustus begins as a magician of normal consequence in terms of the setting of Marlowe's play. Through Mephistophilis, Faustus strikes a deal with the Devil to become a great magician, one with otherwise unheard of powers. To determine what one "can make of Faustus's exploits as a magician," one must know the conditions upon which he agreed to the deal and the outcome of what is really granted to him.
Faustus desired ultimate knowledge and, with it, ultimate power, both to be delivered to him through the ultimate degree in magic:
I'll be great emperor of the world,
And make a bridge thorough the moving air,
To pass the ocean with a band of men;
The Emperor shall not live but by my leave,
I'll live in speculation of this art [of magic],
Till Mephistophilis return again.
Faustus is expecting to have demons at his command who will "fly to India for gold" and "read him] strange philosophy" of the arts of magic. What is it he actually receives from Mephistophilis during the twenty-four year span of his life on Earth under the terms of his Devil's deal?
What Faustus really receives from Mephistophilis in this devilish deal falls into the category of trivia and pranks. For instance, in Act III, Scene ii, Mephistophilis--Faustus's constant companion--renders Faustus invisible so he can shadow the Pope and take food and drink right from the Pope's very hands.
Faustus does not attain what he expected from the Devil. He was hampered by the frivolous nature of Mephistophilis’s limited powers and overriding instructions from the devilish Prince of Darkness. Therefore what I make of Faustus's exploits as a magician is that he wasted twenty-four years of aspiration to reach beyond the bounds of human knowledge to the wisdom of the cosmos upon the frivolities of the dark humor of a sorely limited life and freedom--a limited life disguised as opportunity.
As is true for everything about Dr. Faustus once he has sold his soul: his magic looks good, but lacks substance. Faustus's plan was to exchange his soul for all kinds of worldly goods: money, power, lust. And he got those things, up to a point. But when you look "behind the curtain" (apologies to The Wizard of Oz), you see that everything he has gained is just smoke and mirrors. In the end, there is nothing lasting and real on which to build his life. He ends up with nothing but the metaphorical flowers he's pulled out of his sleeve, which don't even smell very nice and which wither immediately upon hitting the air.