So you need the best way to get Stardust...stat!? This is the page for you!
Surprisingly, Stardust, even though it's a relatively low-level Rare Item in CastleVille Legends, can be pretty hard to come by. But here I've outlined all of your options for collecting Stardust, so that you can execute one of them repeatedly, or all of them simultaneously - your choice!
If you were fortunate enough to have been around for the Easter 2014 Seasonal Event, you'll likely have a bunny that will produce 1 Stardust for you every 9 hours. Otherwise, adventuring is the way to go:
The Well of Wishes can give you 100% chance of coming back with Stardust, if you use the right adventurers. Both Bayoo and Greenleaf have a 60% chance of bringing back Stardust, and pairing either of them with either Bluebelle or Willow will bring your odds up to 100% every time.
Or, for different odds, check out these folks:
Well of Wishes
Everyone else has 25-30% chance of bringing back Stardust, so putting any one of them with either Greenleaf or Bayoo would give you a very good likelihood of bringing home the bacon...er, Stardust.
But what if you don't want (or have time) to commit to an 8-hour adventure? Well, chances of bringing back Stardust will be slimmer, but your next best option is an 82% chance, which you get if you use Tanya and any two others at the Fairy Falls (3 hours). Bonus is that you get a pretty good shot at bringing back Everlasting Bubbles, too!
Your third best option, which will net you just over a 50% chance of coming back with Stardust, is to send Magnus and any 4 other explorers to the Frost Owl Spire. However, this adventure takes 12 hours, so I would definitely recommend it only as an "in-addition-to" strategy, and not a first choice.
Your fourth and final option is the Elemental Nexus. The best odds you can muster here, though, are about 23%, by using Bayoo and 3 others. Really, if you're going to send Bayoo out, he'd be much better used at the Well of Wishes (considering both it and the Nexus have the same exploration time). So this suggestion is really only for if your Well of Wishes is already busy, and you don't mind taking a long shot.
Remember, if you would like to see a table showing all of the odds for all of the characters at a given Place of Legend, you can always do that at that place's page. There's a list of all of these pages that I have complete right here!