Early on I would recommend going for the highest item level.
Once you start getting same item level pieces you can start using raidbots to sim for the best piece.
General Offensive Ranking: Crit = Vers > Haste > Mastery
Mastery is a very strong defensive stat if you can take advantage of it for certain abilities that can be dodged.
Critical Strike: Increased chance for attacks and heals to crit. Works well for Brewmaster due to Celestial Fortune which also always works on absorbs.
Versatility: Increases all your damage and healing done, as well as decreases all damage taken.
Mastery: (Mastery: Elusive Brawler) grants you a stacking buff that increases your chance to dodge until you have successfully dodged. Mastery also increases your Attack Power.
Just like previous expansions, the difference between races is generally very small, and therefor I recommend picking whichever race you like the most.
Some races perform slightly better for specific situations.
Night Elf for Shadowmeld if your plan is to run Mythic+ and skip a lot with your group.
Blood Elf for Arcane Torrent if the content you run has something meaningful to dispel(generally Mythic+)
Pandaren: Panda can be great if current food buffs x2 outweighs other racials.
Vulpera: Bag of Tricks is a solid damage ability that scales with damage amplifiers.
Generally you would want to pick something that has crit, vers or both.
I would recommend to sim to get the best offensive result.
As mentioned under stats, mastery has its uses so this is something you will have to decide for yourself if you need the defensive value.
Healing Potion: Refreshing Healing Potion
Rune: Draconic Augment Rune