I had to buy two deco-den sets from Yukie because my sister wanted the same set too!
I've been watching many deco videos and have noted down a few useful steps:
1) Start with main features first e.g. big heart or rose
2) Add the border
3) Fill in with bigger pearls or gems then fill with medium sized as much as you can
4) Fill in the gaps with the smallest pearls or gems
If you add the border first, you won't have room to add the main features and it will look cluttered inside the border.
If you add the border last, it will look wonky because you have to move around the pearls or gems that are already there!
I used some all purpose glue by 'Bond' (I think). If you're not using the actual Japanese glue usually other glues get everywhere but once your object is cluttered with pretty stuff, you'd barely notice any glue!
Hope it helps!!