ShpeeismePlaying matchmaking as it is right now is not a good way to get into competitive 6s but I'm going to add you anyway since I have some leftover beta invites.
If I were you I'd go to tf2center and start playing highlander lobbies as scout. There you're not a very important class so people won't get mad at you if you don't do well and it's a good way to see what your skill level is at compared to the tf2center community. If you do alright in a couple lobbies I suggest you move on to 6s and play a not very important class there (such as roamer or scout). If you do alright there you should play the class you want to main in 6s lobbies and get as good as possible at it. You'll make friends from tf2center and you can join or start a team with them. That's how it went for me. You can also add people from ozfortress, the Australian tf2 league who are looking for players and ask to trial (try out) for them. Etf2l has a recruitment page where people can post when they're looking for players or teams but I couldn't find that on ozfortress. It should be there if you look hard enough.
Also play a lot of MGE and DM. If you wanna be a medic main it's not neccesary but still very useful. Good luck!
Hi Shpeeisme, i was actually looking at being a medic main (since i can't hit a shot to save my life) and i've done a bit of research too. i've watched shade do some demo reviews of other medic mains and also some youtube guides by Slin. from this, i've learnt heal order, and how to use ubers properly. i'm not sure what MGE and DMs are though (relatively new here if you couldn't already tell :P) but i'll do some research.
Anyway, thanks for the positive feedback!