Maybe it would be cheaper to buy the 'Spellbound Bloom'. It's a huge 3x3 pink/red/purple single flower. Don't remember it's price but assure it resolves the spellbound dew collection. As I have it already it's not available anymore in my Market, maybe it's offered in yours as you don't have it yet.
Buying the Unicorns you would spend more as only one drops 4 spellbound dews per day.. so you would need the others to to have a worthwhile collection.
The Spellbound Bloom drops 2/3 every 2 hrs.