With the Z97 chipset there is a ridiculous amount of options for motherboards. You have the expensive motherboards with most of the advancements and multiple features included, but features still vary a lot and it is best to do research to find the motherboard which has particular features that interest you the most (and that you are going to use). A expensive or top-tier motherboard isn't really needed to have a good gaming PC.
The clear advantage of Z97 is no correction revision has been needed for this chipset at all like it was with early generation chipset equivalents, a lot of motherboards have good in-built sound cards (not necessary better than sound cards, but better than built-in sound cards in previous generations), improved USB 3 and Sata III/6GBs.
As for me I went for a striped down motherboard with less features that I really wouldn't want (or even have any intention of using) and as for the introduction of Sata Express and Thunderbolt they are too early generation and a bit to specialist for my liking at the moment as not many devices have a significant reliance on those features. Also I haven't quite been brought in by the M.2, mSata or other unusual SSDs, although I've looked into these and some others a bit though.
My reasons for choosing my particular motherboard was that it had some features from more higher-tier equivalents which I did like such as its sound card, I did like the Ethernet port as well as the motherboard's overall layout for general layout and selection of rear ports which were to my liking.
As for RAM 12GB would simply be incorrect given modern Desktop PCs are a lot more sensitive to mismatched RAM and 12GB is more for triple channel setups from the first generation i7 CPUs with the X58 chipset where the configuration is either 6x2GB or 3x4GB. Intel never continued the triple channel RAM setup and replaced it with quad channel instead.
For recommended RAM for a gaming PC I would recommend 8GB at the very minimum, but for the price 16GB is generally a lot better even though you might not require or manage to use an application which would make most use of 16GB.
My choice in relation to choosing 32GB is because I wanted to go all out with my upgrade from my previous system (as I have such luxuries to do so), but if I feel there is a performance benefit of having 16GB instead I can just remove two modules and I'm fine.
