Board Thread:Bloons Wiki and BTD News/@comment-85.75.116.178-20161019155209/@comment-24545666-20161120133354

The decals are for two types of people:

a) battles vets who've been playing a long time and have nothing better to do with their medallians,

b) people who buy the decals before the tower upgrades to look cool (or just because they felt like it)

Personally, I would save all the medallians for the tower upgrades first, then go and by decals (after all upgrades are finished).

On the note of whether to send bloons as quickly as possible, I can only say that: it really is your choice. As you keep playing, you'll find your ideal combination between offense and defense. Some people don't send at all, preffering to stay with defense or banana farms; some do a mix; etc. Early levels, though (less than 250 battle score), just spam until you start losing lives. XD