The sun has come down by now, and it's pretty chilly outside--so naturally, most people are going to be in their homes. Your best test subjects will be in the neighborhood.
You stroll into the streets with upper-middle class houses lined up in every direction. You're tempted to pick a house right now, but you consider that the deeper into the subdivision you go, the more isolated you will be from the outside world; you'll have a more controlled environment to work in. Your feet start to get tired by the time you reach the near-core of this enormous network of houses; and the houses themselves start to look older and less lustrous. You've obviously gotten to the section that was mostly built during the 70's and 80's, and features homes with more unorthodox layouts.
Finally, one particular open garage catches your eye; inside the garage are boxes and tables and chairs and... something about the way it's all laid out screams "aging family" to you. By 'aging family', you mean that there is probably a mother and father in their 40s or 50s, a teenager, and probably a prepubescent child. A good representation of a bunch of age groups, in other words; something that could yield much more fruitful data. Satisfied with this hunch, you casually stroll right up to the door.
As soon as the door is opened for you, you can tell your assumptions are at least a little bit off-base, as you are met by a 30-something looking woman who is probably a mom. She is curious as to who you are. Time to see if the sapphire's powers can dig you into an extremely unique situation with ease; it's now or never.
"Hello, ma'am." You extend your hand.
~Accept me into the house as though I were a good friend of the family, even though you are aware you only just met me~
"Nice to meet you!" The woman shakes your hand. "My name is Lindsey."
"Eric." You smile as you are let into the living room.
There's a slightly older-looking man sitting on the couch, who has his head cocked back at you; and gradually stands up to get a good look at you.
"And... who might you be?" He asks, a look of particular skepticism on his face.
You blink for a second, not sure how to react at first.
"I'm... Eri--"
"I know you're Eric." He cuts you off. "But what's your business here? And what was all that about 'accepting you into the house as if you were a friend'?" He takes a step forward, somewhat hostily.
"Honey, he hasn't said anything like that." Lidnsey jumps in, taking a protective step in-between the two of you.
As you suspected, the sapphire command you placed on his wife didn't have an effect on the husband, because it wasn't directed at him. What's worse, however, is that while those affected by the command are not even aware of hearing it, the command will be noticed by those within earshot. This sapphire may indeed be all-powerful over a single mind, but it's clear that you will still have to use its power tactically.
~Forget your concerns about me~ you command, as you step out from behind Lindsey, ~the both of you will agree that you have no worries about me being in your house; you have no suspicion, and in fact are happy to have me around without questioning me~
With that instruction made, the tone of the room cools back down--and Lindsey sighs with relief as she shuts the front door. You ascertain that the husband's name is Dan, and then quickly move on to the next command.
~Is there anyone else in the house, and if so, where are they?~
"Just Emily, our daughter." Lindsey replies. "She's up in her room."
"Cool." You nod, leaning against the couch; trying to act relaxed. You figure that you can obtain more information just by asking them, without having to use the sapphire. "How old is Emily?"
"Shesh ffrirtheen." Dan answers, having returned to the show he was watching and his mouth full of cheetos.
"Baby! She's fourteen!" Lindsey crosses her arms.
Dan's eyebrows shoot up.
"Christ." He rubs his forehead. "I don't know what I'm gonna do if she gets any older..."
So this is a younger family, with only one teenaged daughter. Your predictions were slightly off, but this homestead appears more than apt for what you want, so you decide to stick with it.
"Eric, sweetie," Lindsey takes a few steps closer to you, "I've been wondering, what's in those bags you're holding?"
"Oh these?" You hold them up a bit; noticing that they're too thick to be seen through.