Hi there,
I now have a level 70 mage that took me a year of casual playing. Here is my advice if you want to focus on PvE play (like instances or questing):
1) Go for the INT gear and spell damage gear (if it exists). After INT, stamina is important to make you less squishy.
2) Play PvP battleground, but keep the honor and tokens for later. I only purchased 3-5 non-level-70 battleground items ever. Some of those pieces lasted me a long time, so they are worth it. (And some of them were poorly selected.) I wouldn't pimp out totally in PvP gear. When I think about how long it took me to earn 30-50 WSG or AB (Warsong Gulch or Arathi Basin) tokens, I regret the time I put into it.
The PvP gear is nice to have, but if I rolled another character, I wouldn't bother struggling to collect tokens until level 70. For the most part, PvP gear is geared for PvP play, which isn't necessarily fantastic for PvE.
I do recommend playing PvP though to learn how to play your class and learn how to react quickly. But don't sink too much time into it. Also, you'll have the most fun when you are in the highest or second highest level in your group. (For example, if the group is 20-29, playing at level 28 or 29 is fun.)
3) Do instances - your best gear is from instances. There is also good stuff that you get while questing, but instances overall are better. I used to be obsessed with collecting the quest first, but there's no need to stress about it. Go forth and enjoy!
4) Remember the Auction House. I like to keep my eyes open for good deals, but only stuff that is 1-2 levels above you. I do remember purchasing a nice staff for 8 g at level 30 or something, and that was a good purchase. Slurge once-in-a-while for something nice. I remember wearing the same weapons and robes the longest, so you might want to get solid pieces there.
5) Check your current gear often. If an item is 10 levels below yours, it's time to replace it quick.
6) Don't bother so much with resistances gear - keep it if you got it, but don't spend money on it. They are usually situational pieces that you put on for special circumstances. (For example, fire resist gear if you are having a hard time defeating a fire elemental.)
7) If you are a tailor, some of the robes will last a long time, so it's worth it to make.
And most of all, have fun. You'll be able to gear yourself quite nicely on quest items and instance drops. I agree with the previous poster, you will be swapping your gear so often, so there is no need to carefully plan your gear upgrades.
Good luck!
Edited, Mar 6th 2008 4:55pm by alitakorgath