Curious about PvP vs PvEFollow

I have a troll mage, and I am leveling with the bonus from the recruit a friend deal because I had my friend invite me when I started my new account. As a brief background, I haven't played in a couple of years, as a frame of reference tier 4 was the highest when I used to play. Now I'm hearing of tier 10. But as I said, I am stampeding through the levels and in a week or so hope to be level 80. My friend does mainly PvE like raids, but I've always been more of a PvP guy myself. I was wondering if I could pick your knowledgeable brains as to whether once I hit 80 should I jump into PvP and try to earn that equipment, or should I go PvE for a bit and get some of that gear. As much as it pains me to admit, I feel as if PvE is the more sound decision because I won't even have a full set of blues when i strike 80, right now I am so focused on leveling I could care less what my gear is as long as it has stamina and intelligence. So my next question to you is that if you agree with me about the PvE idea, what is a good raiding build for a mage? and what raids would I be looking to go on? like which ones have the best/ most gear that a mage would roll for? I'm sure I could research this all myself and I plan to, I just figured a community of mages would know best. And I have read the mage sticky post on this, I am asking all of this because I want to know what real people who have been playing mages think on their own, not what they collectively think. I am up to hear any suggestions, anything from a frost fire build to an arcane build. Also the gear thing I want to see what everyone thinks. Thank you for any input you give me, it will help me a lot.

Okay, thank you so much boquaz for that response, it confirmed a few things for me. I was thinking queing up in the LFG for random dungeons, and I believe I have the whole heroic thing down, higher drop rate, but harder. And what do you mean by weekly raids? I seem to remember some raids having something like a respawn rate. I don't know how to phrase it, but like you couldn't go in and complete the dungeon daily, there was like a cool down before being able to run it again. Is that what you're referring to or am I making myself seem completely uninformed? And the PvP idea sounds great, i have read up on wintergrasp. Now my question would be, how can a mage reduce aggro? Like as far as i see we have almost no skills to lower aggro, and we hit hard enough to **** off a boss. Just adding that to my original set of question, because I see it being an issue. Thanks again!