I tell you my experience. I'm leveling a priest that it's 60 now and since I have also done some instances (and I have full heirloom set with 20% experience gain bonuses) and been very ahead of the guide, I skipped some zones since they were grey quest for me, well it was a real mess. Missing quests because I didn't to the previous to enable the following. Going in a zone then realizing that I couldn't do that quest because I didn't do the starting quest chain, very unconmfortable. In short what I suggest you it's not to skip areas, or make really sure that you do all the quests required (at least) and check carefully the previous zone you'll going to skip to make sure that you won't have problems with struggling finding where to start the quest chain to sync with the guide section.
Heirlooms. At the bare minimum you make sure all the armor pieces upgraded to 110, since this is the lion's share of your experience increase. Neck and Ring upgrades are secondary, but still important due to being able to enchant them. Trinkets can't be enchanted, but you'll want them at max as well, if only to save time by not having to worry about replacing them as you level.
I made one for my guildies but its for the Horde leveling process. One tip that goes for both factions is that you dont need to do all 3 zones to hit 120. I did like 1 and than three quarters of another. But once your 120 you need friendly with all 3 of your factions new reps to unlock world quests so make sure you hit at least friendly with all 3 while your leveling.
REALMS Aerie Peak Aman'Thul Area 52 Arthas Baelgun Barthilas Blackrock Bleeding Hollow Burning Legion Cenarius Dalaran Darkspear Earthen Ring Emerald Dream Frostmourne Garona Garrosh Hyjal Illidan Kel'Thuzad Kil'jaeden Korgath Lightbringer Mal'Ganis Moon Guard Proudmoore Ravenholdt Sargeras Saurfang Shattered Hand Stormrage Stormreaver Thrall Tichondrius Turalyon Wyrmrest Accord Zul'jin Aegwynn, Bonechewer, Daggerspine, Gurubashi, and Hakkar Agamaggan, Archimonde, Jaedenar, and The Underbog Aggramar and Fizzcrank Akama, Dragonmaw, and Mug'thol Alleria and Khadgar Alexstrasza and Terokkar Altar of Storms, Anetheron, Magtheridon, and Ysondre Alterac Mountains, Balnazzar, Gorgonnash, The Forgotten Coast, and Warsong Andorhal, Scilla, Ursin, and Zuluhed Antonidas and Uldum Anub’arak, Chromaggus, Crushridge, Garithos, Nathrezim, and Smolderthorn Anvilmar and Undermine Arathor and Drenden Argent Dawn and The Scryers Arygos and Llane Auchindoun, Cho'gall, and Laughing Skull Azgalor, Azshara, Destromath, and Thunderlord Azjol-Nerub and Khaz Modan Azuremyst and Staghelm Baelgun and Doomhammer Black Dragonflight, Gul'dan, and Skullcrusher Blackhand and Galakrond Blackwater Raiders and Shadow Council Blackwing Lair, Dethecus, Detheroc, Haomarush, Lethon, and Shadowmoon Bladefist and Kul Tiras Blade's Edge and Thunderhorn Blood Furnace, Mannoroth, and Nazjatar Bloodhoof and Duskwood Bloodscalp, Boulderfist, Dunemaul, Maiev, and Stonemaul Borean Tundra and Shadowsong Bronzebeard and Shandris Burning Blade, Lightning's Blade, and Onyxia Caelestrasz and Nagrand Cairne and Perenolde Cenarion Circle and Sisters of Elune Coilfang, Dark Iron, Dalvengyr, and Demon Soul Dawnbringer and Madoran Darrowmere and Windrunner Dath'Remar and Khaz'goroth Deathwing, Executus, Kalecgos, and Shattered Halls Dentarg and Whisperwind Detheroc and Shadowmoon Draenor and Echo Isles Dragonblight and Fenris Draka and Suramar Drak’Tharon, Firetree, Malorne, Rivendare, Spirestone, and Stormscale Drak'thul and Skywall Dreadmaul and Thaurissan Durotan and Ysera Eitrigg and Shu'halo Eldre’Thalas and Korialstrasz Elune and Gilneas Eonar and Velen Eredar, Gorefiend, Spinebreaker, and Wildhammer Exodar and Medivh Farstriders, Silver Hand, and Thorium Brotherhood Feathermoon and Scarlet Crusade Frostmane, Ner'zhul, and Tortheldrin Frostwolf and Vashj Ghostlands and Kael'thas Gnomeregan and Moonrunner Greymane and Tanaris Grizzly Hills and Lothar Gundrak and Jubei'Thos Hellscream and Zangarmarsh Hydraxis and Terenas Icecrown and Malygos Kargath and Norgannon Kilrogg and Winterhoof Kirin Tor, Sentinels, and Steamwheedle Cartel Lightninghoof, Maelstrom, and The Venture Co Malfurion and Trollbane Misha and Rexxar Mok'Nathal and Silvermoon Muradin and Nordrassil Nazgrel, Nesingwary, and Vek'nilash Quel'dorei and Sen'jin Ravencrest and Uldaman Ravenholdt and Twisting Nether Runetotem and Uther
From time to time we may also collect personal data from other sources that the data subject – for example when we identify beneficial owners within AML process or if you provide us personal data of other persons. In many cases providing information included in this policy to such persons proves impossible or would involve a disproportionate effort. We appreciate if you may help us to be transparent to such persons on processing of their data. Such data are not used for marketing purposes.