hello all,
what is the most common sort of trombone? ive seen alto, tenor and bass all in different keys and im very confused. please help me!

more than likely you've seen Tenor trombones.

yeah thats what i thought. So if i were to buy a tenor Bb trombone that would be the most usual thing?

The most common type of trombone today is the Bb teneor trombone. However my bandmates always mistakenly/purposely use C tenor trombone scores... Either they really don't know that they are wrong or they just do not want to play one note higher.
Conn tenor trombones are the best I have seen. I've heard rumours about Bach trombones having a huge lot of resistance.

I'm a bit confused by what you mean by C tenor trombone scores...
Trombones are generally written in concert pitch, or more rarely Bb treble. Is this something they do differently in Singapore?
Last time I was there, I got to play with a group at the National University of Singapore and everything we played was standard bass clef concert pitch.
Are you referring to tenor clef? If so , why is that a mistake? I read tenor quite regularly in the group I play with. I also read quite a bit of alto.

If you are just starting out a Tenor trombone will probably be best.
But if you have a bit of experience or even if your just new, a Tenor-Bass trombone, a Bb with an F attachment, will probably be best. try a yamaha James Morisson trombone, this is what i play, for the time being. its a great student trombone and has lasted me a few years, although i am currently upgrading to an Edwards.

Just because a trombone has an F-attachment, that does not make it a bass trombone. Also, there is no "Tenor-bass trombone". Just correcting the terminology as to avoid confusion.

If a trombone has a .547 bore, valve or not, it is most commonly referred to as a large-bore tenor trombone, for example.

Tenor B flat trombone is the most seen one .
But I think buying a trombone with trigger is better
all trombone scores ought to be in concert pitch