Well, if I calculated correctly, you don't have to purchase any Welcome Amiibo items because you could still get 80% of your catalog done, but... I've made a decision to purchase as many Amiibo I can get. I don't really care for the ones that have multiples of the same character (for example, there is one summer Isabelle figurine, one Winter Isabelle figurine [which I have obtained both just because I can get both of her outfits], then 7 different Amiibo cards throughout Amiibo Card Series 1-5), I'm not getting all 9 Isabelles because why scan a card if they've got a figurine? The figurines have the RV, the cards don't, so it would be pointless purchasing them, unless if the cards were from those series packs, and then you just trade them for a different character, I suppose.
I don't mind either Japanese or English cards, as long as they work when I scan, which they should because they're not region-locked. I've compiled a list of Amiibos I have, Amiibos I don't have and a list of Amiibos I'm searching for next.
Top priority are the Amiibos that give out exclusive furniture, or items that I will use for my home. The next priority is the search for villagers that will fit my ACNL town, the villagers that will fit my ACNH island and any character I'd love to receive their poster from Photopia/like to scan at The Roost.
All the while, I'm spacing out all the times I search for them, my bank balance is more important, especially now I've got some sort of collection going on. I'm not constantly searching for them every single day, but I will eventually get one of each character, plus the crossover villagers (Sanrio, Monster Hunter, Splatoon and Legend of Zelda)!
Which also is awesome that I am collecting the Splatoon Amiibo since I will also use them for Splatoon 3.