This is how I completed the 3rd/Final win of Challenge 27 in Merge Magic. I used 11 gems to buy a pink energy orb and I used 50 gems to extend my time to get that one last second to finish. I probably could have finished without the time extension if i hadn't messed up harvesting from the ancient tree.
Also, full disclosure, i had the full speed boost from the season pass. I'm pretty sure the time extension would be necessary without it, even if everything was handled perfectly.
The big takeaways:
1) Completing this final win requires spending at LEAST 11 gems on a pink orb.
2) Don't bother spending any gems unless you get the 2 Level 2 Piles of druid stones first.
3) Be prepared to spend a total of 61 gems (11 for the pink orb, which is necessary, and 50 to extend time in case any little thing doesn't go perfectly.)
I would have preferred to post the video without the time extension - I do think it's possible - but I'm done spending compasses on this. It was worth the gems to me to just be done.