Just to pick up a question that wasn't fully answered: yes, the trades (=trade paperback, =TPB, ='book') collect a number of individual comics together and often include a couple of pages of bonus stuff such as a cover gallery or sketch art. The downside is that they're usually released a couple of months after the individual issues have all been published.
The IDW main continuity series is Infiltration -> Escalation -> Devastation. Stormbringer was published between I & E but runs roughly parallel to Infiltration in the continuity, ending just before the latter half of Infiltration #6.
The Spotlights are set at various points in the recent or distant past of the main continuity, and all of them take references from and give input into the main line to a greater or lesser extent. While they're well worth reading, they're mostly ancillary material and can cheerfully wait until you've read the main line, when you'll be at least familiar with the events that the Spotlights are meant to be shedding light on.
As far as the relative importance of the Spotlights go, some are more closely connected to the main line than others. I'll list a couple of things they link to so you can see which you're more interested in, if you want to...
WARNING:
MILD SPOILERS
Shockwave: Explains the Ore-13 / 'super Energon' on Earth, sets up Bludgeon's role in Stormbringer and the archeological dig in Escalation #5.
Nightbeat: Details some events prior to Nightbeat's arrival on Earth in Escalation, which may prove to be very important in Devastation. Linked to the Galvatron / Dead Universe plotline, suspected to be linked to events at the end of Escalation #6.
Hot Rod: Mostly standalone story, will probably have future ramifications (especially for Hot Rod) but not yet connected to the main line.
Sixshot: Introduces an extinction-level alien threat (besides Sixshot himself!) which will almost certainly reappear in Devastation after getting a panel in Escalation #6.
Ultra Magnus: Sets up the history and architect of The Machination in the main line (near-universally believed to identify the 'talking head' in Escalation #5), sets up Hunter's situation in Escalation #6 and hints towards events which will unfold in Devastation.
Soundwave: Links to Sp: Shockwave and Stormbringer, references the archeological dig in Escalation #5 and sets up Skywatch's possession of certain TFs in Escalation #6.
Kup: Mostly standalone, referenced (inconsequentially) in Devastation #1.
Galvatron: Sets up the Galvatron / Dead Universe plotline which will almost certainly become a major point in Devastation and onwards, apparently ties to Prime's 'vision' in Escalation #6.
Optimus Prime: No firm info yet.