Please note stats may vary entirely from player to player depending on what your current stats are. This could mean Mastery would be your worst stat. Please use the tools shown in stat discussion to get the most accurate results.
Mastery = Haste > Vers = Crit
Mastery = Haste > Vers > Crit
Mastery (Mastery: Harmony) - Each HoT we have on a target increases our healing on them by a moderate amount. You will always get value from this, especially when dealing with high single damage. It is also strong when ramping and using cooldowns during high damage.
Critical Strike - Increases the chance for each heal and damage ability to crit, this includes all HoTs.
Haste - Like other classes haste reduces your cast time and lowers your GCD. In addition it also benefits our DoTs and HoTs by giving use a partial tick at the end of their duration.
Versatility - A fairly bland stat it increases your damage / healing while also reducing damage taken.
Your stats may vary heavily as to what is best and worst, the best way to know what is strongest for you is by using one of the tools available which I will list below.
Twig it - https://rebrand.ly/Twig_It this is a spreadsheet from Torty a well known healing thoerycrafter.
WoWAnalyzer - https://wowanalyzer.com/ an amazing site for reviewing your performances and figuring out what stats are best for you.
HealerStatWeights Addon - https://wow.curseforge.com/projects/healerstatweights
For Alliance the best race would be Nightelf due to its ability to shadowmeld within dungeons and it has an okay passive for raid content. Honorable mention to Kul Tiran their passive is strong for the raid but slightly weaker all round race if you are wanting to do M+.
As for Horde the difference between a few races is very minimal so it mainly comes down to preference.
Troll - Berserking gives you an additional cooldown to ramp with.
Zandalari Troll - Embrace of Pa’ku is the highest throughput passive racial but offers very little elsewhere.
Highmountain Tauren - With this race you gain 1% vers and a strong mobility cooldown which may come in handy on occasion, although as a druid this may go to waste.
Haste Enchant Weapon - Quick Navigation
Haste Enchant Ring - Pact of Haste
Mastery Enchant Weapon - Masterful Navigation
Mastery Enchant Ring - Pact of Mastery
Haste Gem - Quick Owlseye
Mastery Gem - Masterful Tidal Amethyst
Flask - Flask of Endless Fathoms