Well all can be useful at different times - Depending on how you want the game to unfold - But this is a few general observations - mixed in with my years of playing experience of how I feel traits have their uses.
Financial - Is always a good trait especially for lower level players - easy advantage without needing particular style to adopt (comfortable Cottage Economy) and roll on from there
Philisophical - I think this edged a recent poll - not certain though - Obviously great for GP farming and overall gives you a whole host of good GP production.
Imperialistic - THE Rex'ing Trait - Great for fast expansion - Long term no major role - but the early advantage can ride itself through the game so long as you can control your economy efficently
Spiritual - The Dimplomatic trait - This has the obvious advantage of no anarchy - which is always useful, but is mainly great for being able to agree with any demands for changes of religion and civic as required keeping more civ's happy.
Cultural - I like this trait - it has quick early advantages of gaining land and blocking its way and expanding - in many ways a good general trait without any 1 exceptional function - Long term the culture bonus is worth very little, but over the game you will always do reasonably well with this.
Industrious - A tricky trait - especially on higher levels - it does have a few advantages late on, but unless you are going to work on many wonders, this can seem a little unuseful - although I do like this in conjunction with Philosophical.
Expansive - A solid trait - helpful to get cities going, and has some fairly useful half time buildings - much like Charismatic - will not win you or lose you a game, and I find you can't really plan a game specifically to this trait but nontheless will always do you no harm.
Charismatic - Useful early on for the happiness & health bonus allows you to use Slavery better - and has a nice effect regarding reduced xp - not IMO a game decider, but for militant leaders this is always a very useful trait to have.
Aggresive - Considered these days a weaker trait overall - Always useful particvularly I feel in longer games where the bonus lasts longer with gunpowder units. Good for Barbarian defence early on too - I still would say though if I was looking for early conquering, this is a very useful trait - although it tends to be quite 1-dimensional in how it forms.
Protective - A very frustrating tech to conquer - but to use - good for only needing a very limited number of units to hold a city - I have to say this is overall my least favourite - although some rave about it - although like certain traits mentioned above - I don't see it as one where you have an obvious plan - and the other trait is likely to determine the game strategy.
Heh, I hope I haven't forgotten one!
I would say for newish players then Financial is nice and comfortable until you get used to the economy side of the game - possibly with Imperialistic or Charismatic. But the key to deciding what you should use is as I started this off with - How do you want to play the game?
Good Luck!
