Great Gourmand of The Ruby Feast

Are you a dummy like me who finished the questline but threw away the food from the first quest or two without sampling it?

Just return to the Ruby Feast every day. To the left of Rumiastrasza is a table with food on it which changes daily. Eventually the food you're missing will show up again.

Table is to the rightside of the dragon. (Table is at /way 61.07, 10.85 - By merenhuiske)
Food is just sitting there for the clicking.
You can have 3 feast foods at once, so if you still have buffs from yesterday or buffs from the food you got from one of the quests then you can choose one to click off and grab your desired buff. You can buy the foods on offer from the greeter at the podium too.

If you seem to be stuck on a particular Chef (and therefore, keep getting the same foods), it looks like you need to do whatever quest Rumiastrasza offers. They might also possibly be tied to the chefs available each day, so if you are stuck in the middle of the quest chain, you might have to wait for the day the chef who's quest you haven't done shows up? (Chef appears to be random, so food and quest is as well, really not sure about that with quest changes.) You get Recipe: Hoard of Draconic Delicacies when you're done with all of them (One per day).

They start with The Ruby Feast! You can fulfill the achievement requirements through the tables or the quests, they both work.
(They changed the way this worked when they opened the raid, for those of us confused by only ever having seen 1 quest. First few weeks it worked differently to now. You only need to do each quest once. )

Vinter Iltheux <High Vintner and Chef of Suramar> serves
1. Rare Vintage Arcwine.
2. Azsunian Poached Lobster
3. Fine Taladorian Cheese Platter
Associated quest - Finest Fungi at the Feast
Leads to - Future-Fresh Fungi

Alchemist Flemthroat <Artisan of Teas and Heavy Pots>
1. Cinna-Cinderbloom Tea
2. Aruunem Berrytart
3. Lemon Silverleaf Tea
Associated quest - All Tea, No Shadeleaf
Leads to - Warm Away These Shivers

Chef Sungshin Ironpaw <Guide to the Ways>
1. Seared Sea Mist Noodles
2. Fried Emperor Wraps
3. Roquefort-Stuffed Peppers
Associated quest - Hearts of Starch
Leads to - Navigating the Leapmaize

Chef Hearthkiln <Artisinal Floursmith of Shadowforge City>
1. Ravenberry Panacotta Delight
2. Moira's Choice Espresso
3. Picante Pomfruit Cake ! Needed for One of Everything, Please!
Associated quest - The Egg's the Thing
Leads to - Anything But a Breeze

Chef Zab'aji <Reknowned Butcher of Zuldazar>
1. Coal-Fired Rib Rack
2. Charred Porter
3. Highly-Spiced Haunch
Associated quest - The Life of Spice
Leads to - 10,000 Years of Roasting

Chef Guff <Friend to All That Thrives> Thanks Cheffner!
1. Dragonfruit Punch
2. Stonetalon Bloom Skewer
3. Druidic Dreamsalad
Associated quest - The Sea Out West
Leads to - Rambling Delight

Chef Coldgale <Fishmonger of Kraken's Reach> If you've been there every day and eaten the food, you've now got the achieve!
1. Mantis Shrimp Cocktail
2. Captain's Caramelized Catfish
3. Venrik's Goat Milk
Associated quest - Savory Seas
Leads to - Delights to Delve For

Quick check for quests you've done -
/s Alchemist Flemthroat
/run print(C_QuestLog.IsQuestFlaggedCompleted(70930))
/run print(C_QuestLog.IsQuestFlaggedCompleted(67047))
/s Chef Zab'aji
/run print(C_QuestLog.IsQuestFlaggedCompleted(70932))
/run print(C_QuestLog.IsQuestFlaggedCompleted(67063))
/s Chef Guff
/run print(C_QuestLog.IsQuestFlaggedCompleted(70957))
/run print(C_QuestLog.IsQuestFlaggedCompleted(67064))
/s Vinter Iltheux
/run print(C_QuestLog.IsQuestFlaggedCompleted(70958))
/run print(C_QuestLog.IsQuestFlaggedCompleted(67065))
/s Chef Coldgale
/run print(C_QuestLog.IsQuestFlaggedCompleted(70981))
/run print(C_QuestLog.IsQuestFlaggedCompleted(67066))
/s Chef Sungshin Ironpaw
/run print(C_QuestLog.IsQuestFlaggedCompleted(70987))
/run print(C_QuestLog.IsQuestFlaggedCompleted(67067))
/s Chef Hearthkiln
/run print(C_QuestLog.IsQuestFlaggedCompleted(70988))
/run print(C_QuestLog.IsQuestFlaggedCompleted(67068))

Am I the only one who got 3 of the same dishes, 4 days in a row?
Silvermoon server.

Edit: I was doing quests every day and also was getting new meal, one day I forgot to do the quest again - and it didn't change selection of meals.
Done it the next day and it changed straight after on the next day.
Maybe you have to complete the quest for meal selection to change, not sure...