Eyebrows are safe and look good on most faces. Lots of girls go for the nose these days but I'm not a big fan. I do like the septum piercing on people who can pull it off but most cannot. Monroes can be cute but again, you gotta have a face for it. If you are shy or introverted and don't want to stand out too much get a weird ear piercing. Industrial, snug, rook, tragus. Those are less common ear piercings and it's still in a conventional location.
A nose stud looks cute on a lot of girls, but adds just enough edge to get rid of the 100% innocent look and give you some confidence. Plus, it can be easily removed if necessary for a job. I don't recommend a Monroe, but that's personal opinion. I've seen very few girls that I thought pulled it off well. Not a huge fan of eyebrow either.
In response to your update, I'd say ask someone that pierces for a living. They'll probably have a good idea. Ask someone who's been doing it awhile, as they'll have seen the most people get the most different piercings.