Lack of carb/tuning exp talking

[KiltedBanshees93GT]

I dont know that this is a problem as such, but another thread prompted me to ask:
On my car, when cranked, the car idles at about 1500, and then drops to 900-1k when dropped into gear (sometimes causing stalling if the car isnt warmed up enough).
I know this shouldnt be normal, and I know the carb is probibly in need of a rebuild, just from looking at it. Are there any simple things a carb novice can do to smooth things out? (I am already planning of ordering a petronix ignitor and coil once the money situations better, but any other tips would be appreciated, ie changing timing/ playing with the current setup etc)
BTW, what should the car be idling at given its current state? I wanna say 900, but I might be wrong. Also, would that be for P/N, or in gear(its never specified,so I decided to ask)
Thanks,

J