what are a few quick tips anybody can offer?
also, which class is the "best" at farming, if farming is even relevant in this game

a few tips off the top of my head

-you need defenses. glass cannons don't work in this game. take a LOT of +life nodes (or energy shield nodes if you want to go chaos inoculation) in your passive tree.
-no specific class is the best. class does not determine your build at all other than your starting area on the tree, any class can use any ability. builds that are verified to be effective can be found on exilepro.com which Curse made in collaboration with Kripparian
-don't get too attached to your first character...you will likely screw it up, and the way respeccing works makes the game very alt-centric
-mobs in this game hit like trucks, but walk like snails and think like chickens. you should be kiting them around often (even as a melee) and not facetanking because they are very easy to manipulate but won't hesitate to smack you down if you take them head on
-flasks are an important part of your build. they're permanent items with consumable charges that will refill as you kill enemies. use them frequently but intelligently. they can be turned into blue items with affixes that are very helpful, so don't be afraid to spend transmute/augmentation/alteration orbs on them as a cheaper way to upgrade your character as opposed to buying or crafting gear.
-when you get to ledge (act 1), fellshrine (act 2), and the docks (act 3), use them to farm a few extra levels to keep your character ahead of the leveling curve
-hoard most of the currency/gems/yellows you find until you are knowledgeable enough to know their values
-read the affixes that blue/yellow mobs spawn with before you start fighting them, or right as you start. some of them can be dangerous and some of them can require a little more brainpower than others (e.g. 'other allies cannot die' aura where you have to kill the one mob or totem that is emitting the aura before anything nearby will die)

these threads on the official forums provide detailed information on the game mechanics and on the crafting system:
http://www.pathofexile.com/forum/view-thread/54003
http://www.pathofexile.com/forum/view-thread/11707

as stated by skinny, DONT USE YOUR CURRENCY, until you have a well made high level character built

chaos, alchemy, exalted, regal etc don't use just save them up

you can use transmutations or alterations to roll flasks and such but don't go willy nilly, just start to compile a good stash of leveling gear etc for your inevitable first death

played for about 30 mins so far, and 1 question i have, what is the currency? i see no gold

orbs

there is no gold orbs are currency

heres the value of them but prices are crazy cause of the month race going on
http://exilestats.com/ex/

Currency system is based off orbs, exalted (excluding the Mirror of Kalandra) being the highest.

Orbs. But when they say don't use any currency, they mean don't use any big currency. Feel free to to transmutes, alterations, and occasionally alchemys if you desperately need a new piece. Chaos/blessed/GCP/exalts etc all save until you're more familiar with the game.