Well, you're in a Tim/Tony comm, so that's a pretty good place to start looking.

We have a very well-defined tagging system that everyone is strongly encouraged to use (you'll see I added a request tag to your post). If you notice, there are various genre tags. If first time is what interests you, then click the genre: first time tag and you'll get a list of posts of stories that contain that element. Obviously, you can't expect each one to be so detailed as to explicitly state 'the development and gradual changes from friendship to something more', but you can always use the back button if fics are not what you want.

Hope this is helpful.