ppl mostly skip t5 these days... so mostly it's a tedious gold / badge of justice farm to get bt/swp boj and crafted gear + some KARA and ZA and you are good to start MH / BT (thought good guilds do swp only these days)... some pvp items are decent in pve too like necks... Kara is easily puggable
Sunwell guilds need people with at least BT gear. You can easily get BT ready with badge/kara/ZA gear.
I think the fastest path (if that's what you're looking for) is a lot of kara, ZA, and heroic farm for badges. Maybe some Sunwell trash farms if those still happen. When you have the good badge gear you should be able to join a BT guild and get everything else you need. If you actually do find a T5 guild then that's just a bonus.
At the Alliance side there are newly formed guilds who are doing heroics, karazhan and gathering people to do 25 man T4 soon and hopefully T5. There is also a guild progressing through T5 content. People are doing any content at Alliance side at this moment.