Okay, I am on the exact same path as you. Got my LMT lower last week, and I've got the upper on layaway.
Aimpoint makes about the best of the reddots. They don't have a fancy selection of dots (it's red, and you can get either a 2MOA or a 4MOA), and you can get magnifiers to get some magnification. Plus, the battery life is INSANE. 40,000 to 80,000 hours depending on the model you choose.
Eotech/Bushnell Holosights are nice too (the Bushnells don't have the roll cage and are not quite as tough, but cheaper). They are very cool, BUT battery life isn't very good (especially compared to the aimpoints). About the same price as an aimpoint, maybe a bit less. Magnifiers are also available for these.
You might want to look at the Trijicon Tripower. It's a type of reflex sight, IIRC, but doesn't require batteries. It has tritium, battery, and fiberoptic illumination for the chevron reticle, and is quite interesting. 1x magnification.
Don't have $400 bucks to drop on an optic? (well, I don't either, so I understand). Truglo makes an acceptable cheap red dot. Nikon makes one that should be good, and a company called Vortex will be introducing one called a Strikefire this summer. They aren't the combat tough/proven optics like Aimpoint, but they will do for range use. There are also the Russian optics , like the Kobra red dot, that is pretty good. Might want to look into that, too.
I personally think PMAGs are the way to go, so I will mainly be buying those. I will also be picking up some GI 20 rounders (because I think they look pretty cool in the AR), and some 30 rounders with Magpul followers.
I would split it up 50/50 between Okay Industries aluminum mags, and Magpul Pmags.
My dealer says that would be prudent, just in case PMAGs turn out to be a flop in a few years like HK mags. I highly doubt that will happen, though.