I guess you do know you can get a mount at 30 now and reduced costs as well ?
My tip is get Auctioneer Suite addon as if you scan the auction house with it on a regular basis ( i go make a coffee while it scans ) it will show you exactly what is worth selling and how much to charge .
Also the easiest way to make gold will depend on server but things like Wool cloth do tend to be worth a lot of gold , on two of my servers it is at least 5g a stack.
Meat drops after you have levelled cooking sell well usually , even low end like Small Eggs can be well worth collecting , on two of my servers i made 20g by level 12 just on eggs.
Take up any of the Gathering trades , skinning mining or herbs all can make decent gold , but even without them meat or fish ( deviate fish at around 1g each ) or cloth drops should make you gold ( wool cloth is about the best at your level )
As for an alt it depends on what you mean efficient? I have tried most to level 40 now except Warrior and the most fun i have is either Mage or Druid , none to me can level as fast as a good hunter can or not at least for me , but saying that the rush to level 10 will give you a little idea of a class and if you like it at 10 then try to 20 as by then you should start to get a feel for a class , but remember many classes do not get to be real fun until after 30 for example a Mage by mid 30,s starts to get very interesting .
If you try a cloth wearer then get tailoring and enchanting as if you follow the guides here you will always have cheap armour usually better than you can get from drops and if you play it right the disenchanted stuff can sell real well .
My hunters usually are never short of gold as i tend to farm mobs that are 6 levels or so below me and still just about green so i gain a little exp , and as i then always have my pet on aggressive all i do is stand and shoot any mob my pet attacks , the result is if its beasts i end up with my bags full of leather and meat plus greens very quickly , or if humanoids i end up with cloth and greens ( i usually end up deleting any vendor trash to make more room ) results vary but i would say i can easily farm 25g in an hour most times.
I hope this helps ?