For the current stuff:
The Death of Optimus Prime, included in MTMTE vol 1, is the starting off point for both MTMTE and RID.
MTMTE and RID take place at the same time, but in different places, RID is set on Cybertron, while MTMTE is set on the Lost Light. There are some rare instances during their runs that things one title does affects the other title directly, but the main plots of both bring major plot events for the whole idw verse into motion that affect both titles during their huge Dark Cybertron crossover event.
The Spottlights were originally meant to tell stories that center around one character, while also introducing plot threads that lead into the main series.
Autocracy and Monstrocity are kinda the start of it all, but it's not required to read them first.
My tip, start with MTMTE and RID, read those volume wise at the same time (MTMTE vol 1, then RID vol 1, then MTMTE vol 2 then RID vol 2, rinse and repeat). Then when you get to the point of Dark Cybertron vol 1 and vol 2, wait and read "Dark Prelude", that contains a couple of kinda bad Spotlights that are kinda important to the Dark Cybertron event. Windblade and volumes 6 of both RID and MTMTE take place after Dark Cybertron.
You don't really need to go back and read all the old material, the important stuff is mentioned and expanded upon in the current books, so if you come across that stuff and don't understand everything or are interested in those events, you can go and check them out.
IF you want a full reading list of everything that's part of the idw verse and in which order to get them:
http://tfwiki.net/wiki/IDW_Publishing#G1_rebootedAgain, it's not required since for a while idw had no interest in keeping their continuity straight and created lots of continuity errors that did not gel with previous material.
The current output is trying to correct that, by slightly retconing and rebooting a few things here and there that no-longer add up.
