1. Which race is the best? does any give them extra stats?
Mithra is built to be a thief with high dex and agility. Tarutaru is second best (and apparently better at stealing b/c steal success is based on INT, which tarus are kings).
2. I see alot of people as Thief/nin, is that the best way to go?
Thief/Nin is pretty accepted as a good combo...iirc, this is mainly b/c of the fact that you can dual wield 2 stat enhancing daggers (primarily dex and agi) and you attack with 2 daggers (as well as with the thief ability triple attack you have a chance to get off SIX hits with one attack).
3. It sounds as if gill is hard to get, well i get alot of pt invites cause i'm a thief? and how much extra gill do i get? will i always be rich?
Gil is a bit hard to get...thieves do have it a bit easier, at level 5 you start getting more gold per drop, and with treasure hunter (15) you become a commodity b/c of increased drop rates (iirc, this includes subjob items) on all treasure...as far as this being reason enough to invite a thief: No, but combined with their other perks, they are a nice addition to any party.
And, you may always be rich...depending on what gear you want and your definition of rich. But you'll definitely have the advantage of being able to farm more effectively when you get bigger.
4. what weapon do I use, Knife, sword? hand 2 hand? which is the most effective with sneak attack?
Up to level 30 ... or 33 ... (whenever you get viper bite weapon skill with dagger) you should use either hand to hand or swords in order to be effective.
Both combo and fast blade stack very well with sneak attack...personally i'm using sword just b/c monk bored me so much that i didn't even want to get up to 15 to make it a viable subjob till 30.
However, daggers are basically the best after that break off b/c of the stellar weaponskills + sneak attack.
5. Do i ever have to tank? do i get aggro alot from sneak attack or trick?
You shouldn't ever have to tank as a thief, you just aren't built for it...however, as you level up, you'll probably find yourself in that role b/t 9-15 in a party (usually, hopefully, just as a back up) b/c thief really doesn't add that much to a party except another sword whacking away at lizards. Luckily for me i did WAR first to 18 to get sub, so i was able to do thf with a WAR sub ... giving me already capped sword stats, the ability to provoke, and the ability to tank a bit at very young levels (up to 13).
Yes, you'll get a lot of aggro from sneak attack...hopefully you'll have capable provokers that can pull the hate directly off of you.
Trick attack, otoh, doesn't give *you* any hate, but instead puts all the hate onto the person standing directly in front of you...however, the discussion re: trick attack + aggro (and the proper application thereof) is one that is fairly common around here, and answered in several other posts.
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Stealing: Basically, you can steal beastcoins from humanoid monsters...stacks of regular bestcoins go for ~1k a dozen, but once you have access to the silver and gold ones, the money starts to really show itself.
You can also steal other stuff from different mobs...but generally i'll reserve my thievery for mobs that give coins...easily stackable and easy to keep track of.
Thief is probably the hardest job to get up to 15 (for a sense of perspective, I've been in quite a few parties pre 15 (gotten all basic jobs except monk to at least 13...which for clarification sake, i'm not saying i'm a veteran, just that i've been in my fair share of low level parties) and i can't think of being in a single one that has said "We NEED to find a thief!"). In fact, if you step into Valkurm and search for 11-14 you'll most likely find several thieves LFG, probably as many thieves as there are other classes combined.
But, stick it out! It certainly starts to get very fun and tactically challenging after that...just your first half level worth of being able to pull of 100+ damage sneak attacks while the rest of the party is hitting for 9-16 is redeeming enough for the amount of slavery you'll endure up to 14.9999.
Have fun! Enjoy!