The first post includes

As a single point of reference for people doing theorycraft, it might be good to include:

HT glyph healing reduction is additive with GoN. (1+.1-0.5)
Rg glyph healing increase is multiplicative.

As far as I know, all mana-reduction% talents/gear are additive (Moonglow, ToL, Tranquil Spirit, 2t7). (This is memory, not a recent test). I'm not sure about HT glyph. I don't know if Idol of Awakening mana reduction is before, or after talent reductions.

I assume the cast-time reduction from the HT glyph and Naturalist are additive, and applied before haste, but I didn't do a search.

In my opinion, now ive never had even close to 400 haste but i feel that if a resto druid has 5/5 Gift of the Earthmother, it is unnecessary to have more than 300-350 haste, as a resto druid with the BIS gear your itemization should look like this

2500SP
300 crit rating = 14% crit chance
310 haste rating=16% increase to the speed that your spells cast.
1200spirit

I don't feel you should have much more than that of either one. If you get much higher of either one (haste/crit) I'm pretty sure you have to socket for one or the other and that is a mistake. Spell Power is our best stat as it is for pretty much all healing classes, and that is what you should be mainly socketing for. Spirit should be your second choice for sockets due to spirit giving us even more healing through Improved Tree of Life. Although they nerfed spirit regen, it is still a good stat for druids due to our talents. If you have a blue socket and you want the socket bonus for an item which is usually spell power, you should put a 16spell pwr in it. There are a few exceptions where you don't really need a socket bonus of 4crit rating and you are better off just putting in a spell power gem and it isn't really beneficial unless you are lacking intellect in which case you could use a gem like Luminous Monarch Topaz or if you want a bit of spell power and a bit of haste, you can use Reckless Monarch Topaz/Reckless Monarch Topaz. I highly suggest in your red socket/yellow socket, using Runed Scarley Ruby(19SP) and if it is blue socket, using Purified Twilight Opal or Sparkling Sky Sapphire. If you are itemizing your gear to have more than 350 haste rating or 310 crit rating, you are using too much of the stat and would benefit a bit more from gaining a bit more spell power. Please correct me If I am wrong but im usually top out of the druids in my guild that I I raid with(by ALOT), usually 5-10% more healing and I only have 162haste). They have around 400 and it seems like they are way over what they should be at and they are lacking another stat therefore putting out less healing than I do

I would highly advise against gearing with any sort of assumption that you will dip outside the 5sr. While on many fights its both natural and possible to get that extra mana regen, I am under the school of thought that you gear/gem for a worst case scenario. In this case I would gem more to the understanding that I will be continually chain casting, and will not get the extra mana regen during the entire fight. This way, when the worst case scenaio hits (suppose another healer goes down, and there isnt a battle rez to cover him) I will have the mana I need to pick up the slack. In short, I would say that your idea is a poor one at best.

Your GCD (unhastened) is 1.5 seconds in a worst case scenario. Per cast you are only gaining .5 seconds of time if you compare it to a Haste Capped cast time. On paper you could justify it as, "If I were to cast 5 Rejuvenations, it used to take me 7.5 seconds. If I get my haste capped, I could do that in 5. That would give me 2.5s more that I could spend gaining mana!" However, in reality if we are spamming hots, it is very likely that our goal is to cover as many people as possible. We wouldnt stop at 5, we would cast as many as possible until our HoTs started falling off. It wouldnt translate into more time out of 5sr, it would just result in more casts.

In fact, lowering your cast time generally has an adverse effect on your mana regen. Completely unhastened, a druid could fit 6.6 casts off in a 10 second window. Lets assume that this is Rejuvenation which (fully talented and with the Idol) has a cost of 371 mana. 371 x 6.6 gives us a grand total of 2448.6 mana spent in a 10 second window (on average). Lets bring our cool down to 1s. We can now cast 10 Rejuvenations in the same time frame, for a mana cost of 3710...not surprisingly we have spent nearly 1.5 times the amount of mana than we would have. As a recap, simply because we can cast more often, a haste capped druid will need more regen to support chain casting than normal.

As far as your gem choices are concerned, I look at it this way. If you need:
Mana: Gem Int
If not: Gem Spell Power

If you want to match a Socket Bonus...
Yellow (Need Regen): Gem Int
Yellow (Dont Need Regen): Int/SP
Red: Spell Power
Blue: Spell Power/Spirit

But, in the future, questions about how to gem shouldn't go into the Itemization forum. That is for the "Druid Simple Questions/Simple Answers". Each of these specific forums should be kept clean with new information or solid theory crafting, and not to hold peoples hands.

There's already been an answer as to Rawr, but I'm finding myself in the same position.

As a holy priest (My Naxx25 main), there was mostly a focus on Intellect until ~22k mana, then haste/crit, then SP. I started gearing that way as a Tree Druid, and my personal goal was to get through a medium length battle (in 25s) without using my innervate (so I can have it as an emergency for someone else).

I have around 1000 int right now (my armory is fishing gear, so I'm guessing) and it feels right, so I'm getting back to SP.