That is down to your personal preference, though the way Scribe's Grimoire is laid out at the moment you can only have a max of two characters, I could change it to increase the max to four but there is no need if you aren't interested in playing that many in the first place. Ideally a single character would be much easier to start things off, but I do have an arc in mind that would allow us to make two new characters closely tied to our own once they're quite good with magic use. (Think apprentices/students)

Good point on location, for the nitty gritty I think we're best off using a fictional location in a real country/state that way we can keep a more grounded reference of location as well as there wont be a mess of made up country names if/when things get a bit more global, but this is all far thought. As for the state and/or country, do you have any preferences? I can see some advantages for being somewhere in Europe, but the US seems like the most convenient location, as it's pretty easy to reference different parts of the US with its various culture types. (I.E. there is a certain  degree of expectation when it comes to living in Mississippi for example)