You can get great shots of people even on an iPhone. Lighting is the key!
This was shot on an old iPhone 6. If you are shooting indoors the best possible light is the one that is available to you, diffused light by a widow works beautifully but placing your subject next to any light source is the key to getting a flattering photo, really look at how the light is hitting your subject, do you see dark shadows under the eyes? move the light or the subject until the shadows are gone or until you feel the subject looks best, using the flash is the worst and usually will result in an unflattering photo with red eyes. Outdoors on a sunny day you want to look for a shady spot and shoot in the shade but as close to the sunny part as the subject can get without actually being in direct sunlight, think of it this way, if the subject is in full direct sunlight have them take a step back until they are no longer in the direct light but only one step behind it, or you can have someone hold up a piece of cardboard and block the harsh light over the subject, this light produces a very flattering look. You can see from the photo above that the sun is all around the subject by the way the weeds are lit up but her face does not have any real harsh light on it that is because she was under a sliver of a branch from a tree that shaded her face from the harsh light the shot turned out beautiful because of that. Composition is also very important for you to keep in mind. I have seen many shots that could have been great ruined by the placement of the subject in the photo, lighting can be good, the subject can look fantastic but if there is a power line running through their head, an ugly trash can, old beat up car, stray dog peeing {you get the picture} it will ruin the shot! This is one of the classic mistakes everyone makes, even photographers that are just starting out. Always look at the entire frame in your view finder to see everything you are capturing if there is a distraction then move your subject or move yourself to make sure the entire photo will look clean and unencumbered by any distasteful background. The shot below has an ugly chain link fence which we could not get away from as we were inside a completely fenced area so to minimize the fence and focus on the girl I had her sit instead of standing which would have shown a lot more of the fence! And guess where we were??........................................................... A dog kennel! Not 5 feet away from us were cages and cages of dogs, dog supplies, dog crates and a lot of dry ugly fields where the dog training takes place this was the one patch of green luckily the sun was behind the subject and coming down at an angle so I took this shot of this lovely little girl. People have a tendency to want to get the newest and most expensive equipment {and it is fun to do!} but you can get some great shots with what you have if you just pay attention to the details.
Practice makes you better and better so every time you pick up your phone or camera for a picture try to remember to think of the light and the entire frame not just how your subject looks but everything that is surrounding them and it will soon become a habit and your pictures will improve dramatically.