MOTM

hi folks.  i am new here to this forum and am just learning about the
motm system.  

i was wondering if i could get some opinions on how to start building
a modular?

ultimately  i would like build from kits an instrument that has lots
of flexibility and a bit of polyphony.  but with a limited budget
(maybe about a $1000) maybe the best way to start is by building
something like a filter bank to process external signal and then add
oscillators, envelope generators, etc...  

does this seem like a good way to go?  

what are the first must have modules?

any advice would be much appreciated.

thanks-
patch