!!Ok let me start my answer. It is not my final conclusion because I want to go on with my statistic a bit longer. But I will make an edit.!!
I made the task 19 days in a row and I have got following information already (my character has never done the quest before so it is awesome for this question!):
Day 1: Some Experience + Backpack + Achievement "Repenter"
Day 2: Some Experience
Day 3: Some Experience + Backpack
Day 4: Some Experience
Day 5: Some Experience
Day 6: Some Experience
Day 7: Some Experience
Day 8: Some Experience
Day 9: Some Experience
Day 10: Some Experience
Day 11: Some Experience + Backpack
Day 12: Some Experience + Backpack
Day 13: Some Experience
Day 14: Some Experience
Day 15: Some Experience
Day 16: Some Experience
Day 17: Some Experience + Backpack
Day 18: Some Experience
Day 19: Some Experience
Interesting sidefacts and helpful information about the tasks:
In 19 days I killed 448 Furious Fire Elemental (if that is interesting for someone for Bestiary as well).
I always start with the "annoying" tasks. First I do the "fire" part where you get the Firecatcher Urn. You have to use this item on dead bodies of Furious Fire Elementals. Bring Avalanches and put the Firecatcher Urn on Hotkey, because you only have 10 seconds to use it on the body. Then kill and use until you receive the message "Finally, the urn is filled with flames. The urn is a lot hotter now but still cool enough to carry." (you receive this message after you successfully used the Urn on the body 5 times - you know it was successful if you receive the message "The flames of the elemental seem to be sucked into the urn"; unsuccessful is "The flickering flames flinch form your grasp". The Firecatcher Urn transform into Hot Firecatcher Urn.
Next I will straightly go to the "magic" part. It sometimes seems a bit hard to do this task. Two things are important: the order of the sparks you have to use the Empty Receptacle on and WHERE you use it. The right order is: red - green - yellow - blue. Seem easy now, but works not as often and easy as we all would love to ^^. The important part is, like already mentioned, where you use the Receptacle. The problem is, if the Sparks are too fast, you will maybe not catch them even if it looked like you clicked onto them in the right moment. If you catch them at the right moment you get the message "You catch a sparkle of wild fury magic and capture it inside the receptacle." and a quest log update. So I will recommend to keep the Server Log open. Also really easy is if you just lure some of the sparks in a spot where it can't move. Or you can also just provide where it will move and use it right in the moment the Spark enters this sqm. The Receptacle transform into a Filled Receptacle and turns white.
The last two tasks are super easy. I would recommend to do the "mushroom" part next, especially if you are lower lvl. This one is easy and I have nothing special to add.
The last is the "watering" part, where you have to use the Elven Vial on a spot and fill it with special water. You can do this on only one sqm and you get a quest log update and the message "The water seems to develop a life of its own as it pours slowly into the vial.". The Elven Vial transforms into a Filled Elven Vial. I only recommend this as last task because it spawns Leaf Golems on the way. This is only a problem if you are lower lvl, otherwise just ignore them.