First, I'd like to say that I prefer small RP groups. I don't mind having a couple of partners, but large groups tend to get very chaotic very quickly; also, the larger the group, the longer it takes for a given "round" of posts. Second, I should mention that while I do try to be fairly active, I may not always have the muse for a post and sometimes take a while. For this, I apologize in advance. Plus, I know people have lives, so I expect something of the same on my partners' ends. Friendly reminders are certainly helpful either way, I'm sure, if a reply is a long time in coming.
Now, on to the idea. I'll just get this out of the way right off: Harry Potter, but without Harry Potter.
My idea takes place in the canon world, but it isn't focused on the lightning-scarred angst-ridden hero; his know-it-all bush-for-a-head would-be girlfriend; or the underrated spider-fearing chess master she chose instead of said lightning-scarred angst-ridden hero. It doesn't even require a school song, regardless of how many warts your friend Hoggy has.
My thought is an adventurer, perhaps a treasure hunter. D&D comes to mind, but without all the numbers and set in the wizarding world. Imagine exploring massive caverns deep underground, tombs long-forgotten, sacred places where gods were worshipped by the ancients and evil things lie in wait...
My witches and wizards tend to have one very specific skill or set of skills at which they're exceptional, with a mediocre-at-best skill(s) to balance them out. My most common example is someone with absolutely fantastic skills at transifguration who's equally terrible at charms; constantly practicing has enabled the development of a handful of castable charms, but charms in general are very difficult and slow to learn for said individual. The witch or wizard would have some excellent skill at potions, probably decent skill at herbology, and likely mediocre but passable skill at the care of magical creatures.
I feel like I'm saying "my" a lot.
Instead of following the typical path of joining the Ministry of Morons, running a shop, becoming an auror, or writing some novel, manual, or pamphlet that people will only read if required to by their instructors, s/he decided to explore the lost ruins of the world and earn his/her fortune in so doing. Yes, s/he has probably written a book or two or three, but all derived from personal adventures rather than simply reciting what others have learned and regurgitating facts one can derive from a thousand other sources. Supported by facts, of course, but certainly the bulk of such literature would be personal experiences.
And since such a lack of skill at charms can be quite a deadly thing, a partner is unfortunately required. Well...perhaps not required. Magic is nothing if not versatile, and as a serious sort of character (most of the time), s/he would certainly be well-prepared, especially having gained some experience (and, of course, experiencing some very narrow escapes and moments of panic that will never, ever come to light).
Of course, there's the matter of how to go about recruiting such a partner; and of course, there's no guarantee of treasure or even significant pay. The work would certainly be dangerous, and sometimes tedious. I'm not sure many would be interested. They'd probably not want to get their fancy suits and cloaks dirty, anyway. Oh, well. Perhaps it's best to go it alone, after all.
...unless you're actually interested in delving into decrepit dungeons likely filled with all sorts of disgusting and dangerous monsters? Or into the very bowels of the earth itself? How are you at facing inferi? What about the odd basilisk? Dragons? Hm. You're not claustrophobic, are you? Or afraid of heights? You do know some charms...don't you?
It's definitely something to discuss, if you both want to do it. We would, of course, have to decide exactly what kind of ruin to explore. My initial thought when I typed this was perhaps a ruin lying above an unexplored system of natural (or perhaps unnatural?) tunnels and caves ultimately leading to a massive cavern or group of caverns buried very deep. They would have their own ecosystem to an extent, as some such places are wont to do, though of course it would be unique and certainly magical in nature.
Haven't actually made the character for it, but...hm. If I branch off from that story I wrote for the cupcake contest, I could certainly use Benjamin as my MC. He might make a reference to his boyfriend if the subject ever comes up, but of course Ben would be the primary focus for me. And then there would be your characters.