I'd rather not start from the beginning of the IDW run, but would the start of MTME and RID be suitable? My comic book store has trades of both with Dark Cybertron runs too, but they don't have earlier stuff (could just get it online if needs be) so I was wondering if that's a good place to start without knowing what happens prior?
In my opinion, the best way to fully appreciate how vast IDW's story is, you have to go back pretty far... sure, you can start somewhere else, but I feel reading from the beginning instills the full scope of IDW. The earliest IDW comic I have is All Hail Megatron, and there's still pieces before that I'd like to have. Alternatively, you can start on LSOTW, move to Chaos Theory, then read MTMTE and RID.
I see your point in that earlier portions of the story lines have some annoying human interaction, but there are some key items you will miss if you ignore them, altogether. You can read summaries from various sites and then pick up prior the Lost Light taking off, but to really enjoy it all, I would read everything. The most recent Dark Cybertron storyline and Shockwave's actions will not have the same impact unless you have started from the beginning IMHO. Even the Spotlight issues really should be read as well.
I would always recommend the spotlights, they're all good side stories and really help create a bigger picture.
Plot wise, if you don't need everything spelled out for you and can fill in some gaps, vol 1 of RID and vol 1 of MTMTE are good starting points. If you like them and the characters, there's plenty to go back for.
The Death of Optimus Prime is good jumping point. I'd say you could start from the very beginning if not the fact that pre AHM stories were abandoned with AHM, so... You aren't losing too much.
I started with Death of Optimus Prime. Their's stuff before but this is the latest I think that's the starting point.
Just to say, the Death of Optimus Prime is included in the first MTMTE trade (not sure about RID) so you don't have to go looking for it.