You got any friends that are part of a raiding guild? You can probably tag along with a flex run if you read up on tactics beforehand. PUGs you pick up in trade chat often have irrational demands for your ilvl (and wouldn't be able to carry a player).
I would skip most of the timeless isle if I were you since 496 random stat gear probably isn't an upgrade over 496 pvp gear. You could replace 1 or 2 weak pieces of gear that you have though. Also there is a chest that is guaranteed to drop a Burden of Eternity, marked with a 7 in this guide:
http://www.mmo-champion.com/threads/...en-Chest-Guide!
Use this burden on a timeless isle token to turn it into a 535 armor piece, if you're lucky with the random stats this should last you until you get a drop in flex mode.
Also if you have time to watch some tactic videos or read a quick guide you're pretty much good to jump into LFR already. LFR is the PVE equivalent of random battlegrounds though, just so you know what kind of attitudes to expect.
As far as guild go, I would say join some people in their flex mode run (as flex allows for additional people to join) and if they like you and how you play you can ask about joining their guild. There's plenty of guilds out there that are pretty casually doing normal mode and/or flex.