I had a lot of luck with those ones.
Villager was actually what kick-started it all for me! I spent a while trying to hunt down Villager as a Christmas present for Justin because I knew he wanted one. I ended up having to import one from Japan, and after having it sat in my room for a while I kind of regretted not getting myself one too (not that I could have: the site I used had a one-per-person limit) but at the same time was glad I couldn't, because I didn't want to get caught up in the amiibo fad. Around a fortnight later I checked Amazon UK and on the off-chance found Villager going for around ?13 (standard retail price for amiibo here is between ?10-15)! I hesitated, but ordered him anyway - figured I could sell him on eBay if I changed my mind. Glad I acted fast - he sold out within an hour of me ordering him!
I managed to get Marth for ?14.99 on eBay by chance last month! The listing had only been up an hour or so and it was morning UK-time. Swooped in on that, especially as Marth is actually a character I really like and play a lot. I picked up Ike around the same time, and I've Robin and Lucina on preorder to complete the
FE:A characters.
Now I just need to get round to actually buying the game; I loved the demo.
As for Rosalina, I managed to preorder her when she first went up on Amazon UK for ?10.85.
I was so glad. I never intended to get so into amiibo, but I said right back when they were shown at E3 that if they made a Rosalina one then I wouldn't be able to resist buying her.
I'll never have a complete collection either, but I'm happy enough just to get the ones I like best.