Hello ajay,
Regarding precaching:
The worldspawn () function (in world.qc) has been commented nicely (even in original 1.06 source code). So you can quickly see how and what to precache there.
Regarding monster "waves":
Will you use your own maps, or will/shall your mod be playable with existing maps ?
The positioning of "The Gate" is the most sensible thing in case 2.
Which should not be a problem in case 1, because you know the exact x/y/z coordinate.
Once you set your "Gate" origin/position, you maybe want to take a look into the source of the "IQ reprised" mod:
http://quakeone.com/forums/quake-mod-re ... rised.htmlezzetabi coded a "monster-wave" into Entar´s IQ mod.
ezzetabi described that "monster-wave" function in the thread itself and I think this code could be very useful for you.
He uses the position of the killed enemies as "The Gate" for new enemies.
That is the only difference to your idea I guess, which should make it even 'easier' to implement it (with a fixed/static "Gate").
Good luck,
Seven.