Many 'commoners' throughout the Bartimaeus Sequence have some level of resilience. I think the Mercenary is the strongest as he shrugs of multiple attacks by Bartimaeus and lesser spirits. But after that is there an order of resilience, specifically one for the Resistance characters?
We do not really know
The precise extent of the resilience possessed by each character is hard to pin down. For example, Mr. Pennyfeather was able to resist attack by several foliots.
"You are not immune. Neither for that matter am I, but I have withstood the assault of three foliots at once, which I believe is quite unusual."
—The Golem's Eye
In context, Mr. Pennyfeather seems to be referring to his degree of resilience as particularly strong. However, the other Resistance members had not been subject to so violent an attack as Mr. Pennyfeather, at the time of the previous quote.
In fact, we know that the resilience of some of the Resistance members is effective against more than foliots:
The alley was illuminated by a brief discharge of heat and light. The bricks of the doorway looked as if they had been seared on a griddle.
To my surprise the boys were still holding on. Two of them gripped my wrists, while the third had both arms tight round my waist.
I repeated the effect with greater emphasis. Car alarms in the next street started ringing. This time, I confess, I expected to be left in the charcoally grip of three charred corpses.
But the boys were still there, breathing hard and holding on like grim death.
—The Amulet of Samarkand
Here they resisted (the admittedly half-hearted) attacks of a mid-level djinni.
The description of resilience from The Golem's Eye is scarcely of more help:
To some degree, all of Mr. Pennyfeather's friends shared his resilience to magic, but how far this stretched was impossible to say. Because of his past, it was clear Mr. Pennyfeather could withstand a fairly strong attack; most of the others, such as Kitty, had only been gently tested so far.
—The Golem's Eye
We can say a few things, however:
Verroq, the Mercenary, has by far the strongest resilience, as noted in the question:
Trouble was, it was a magical attack, and—as he knew from bitter experience—the mercenary's resilience to magic was huge.
Kitty (most likely correctly) believes Nick to be at least as resilient as she is:
Resilience was not something they knew much of, firsthand. Except Nick Drew, who possessed as least as much resilience as Kitty. But he sat quiet, saying nothing.
Kitty's resilience is likely significantly better than average, since John Mandrake (Nathaniel) called it "impressive"
"I'm glad you're alive," the magician said. His face was gray, but his voice was calm. There was dried blood on his neck. "That's impressive resilience you've got there. Can you see through illusions too?"