Mostly backing Paulbot up here.
DW
War Within Volume #1 was fantastic, but the other 1 and a half were not so great. I'd wait for the War Within omnibus coming out later this year (IDW reprinting DW material) and pick that up. Skip the G1 based ongoing comic, the first two trades are more or less horrible, but they did get better just before the series was cancelled.
Skip Micromasters to save your brain.

More than Meets the Eye volumes 1 &2 are certainly worth it, and with IDW just releasing re-prints, they are a good price now.

Armada and Energon are interesting but far from worth hunting down and paying for, unless you truly loved the Armada and Energon characters in the shows. Even then the comics are radically different.

IDW
It's tough to recommend IDW's main story stuff, purely because it is very much an all or nothing.

I'd suggest Stormbringer as it is easy enough to follow along, the Infiltration, Escalation, Devastation and revelation books are great reads, but not only will you be wanting those four trades, but the 3 Spotlight Trades that tie into the larger story.

It is easier to find trades than the single issues, but if you want to track down some fantastic stand alone Spotlights, Kup, Shockwave, Hot Rod, Ultra Magnus, Blaster, Wheelie and Arcee stand up very well.
If you do get into the main IDW story I do suggest getting all the spotlight Trades, as only Spotlight Kup, Ramjet, Mirage, Wheelie and Blaster do not tie directly into the main story.

If you want to skip the previous main story of IDW (Infiltration through Revelation) and start fresh with Maximum Dinobots (a great starting point) you would benefit reading Spotlights: Shockwave, Soundwave, Grimlock, and Ultra Magnus.

Hearts of Steel was as Paulbot suggested, a great concept executed badly, same for Megatron: Origins.
Only nab Beast Wars if you liked the Cartoon, and you may also be interested in the Beast Wars sourcebook too.

Avoid the first movie comics, Reign of Starscream is passable, but far from necessary reading.

Leave issues 1-6 of All Hail Megatron for now, a trade will be out in April or so, and I think AHM might be best read in Trade format.