I've been playing for about 5 months now, but I'm still a noob. I haven't gotten any character to 50, I think my highest level one is 27. I like the republic side more, feels like where I would want to live irl. My "main" if you can call it that is a trooper, and I really like her. I also like the jedi consular and knight. There are a lot of things in this game that are not obvious to a new player, even just finding out which stats are for my character... it's not posted anywhere that I could find, so I've been guessing. I also haven't done any FPs except with the one friend I know irl who plays. I'm too worried about not knowing what I'm doing and causing a wipe. But I love this game, and am really looking forward to the expansion.
if you hover your mouse over each individual stat, it will show you what they do for your toon. but in general, the main stats are...
strength - warrior/knight
aim - trooper/bounty hunter
cunning - smuggler/imperial agent
willpower - consular/inquisitor
and as far as knowing what to do in flashpoints, this guide
should help you.