which method book would yall recommend for working on sightreading? i have smartmusic, is there anything in there which could help me with sightreading?

borrow anything you can get your hands on. read it. borrow something else. read it.
read stuff you already have, but in tenor clef, or tenor clef down an octave.
read some french horn music, work on sight transposing. trumpet parts?
bassoon music? euphonium parts?
There really is no need to buy music or method books just for sight reading. Between all your bandmates, there is a wealth of material I'm sure people will loan you.

I got to agree with everything Steve said.100% good advice.You have a wealth of material at your disposal with all the different clefs etc.You could waste some money on buying some play alongs and trying to play them first time out but they become useless after you play through them once!!If you want to go that route I can recommend a Bill Watrus play along that somebody once lent me.It had technique work you could maybe use once you've finished the sight reading of it.I'll try get you the name of it soon.Pat.

thanks, i'll do that

or try Blazevich Clef studies
and Bordogni etudes