Is it necessary to place out a spot for all the fishtypes and all the butterflies to be able to get all the fishes and butterflies? I've lost control on how many of those spots I've but out, it could be to many or to few... This is so confusing! o.O

If you look in the manual document there's a list of what spawns with what spawners, and what is most likely to spawn. If you want to be able to collect all types in your 'hood you need to place at least one spawner for each type - not necessarily one of each spawner, but at least one spawner for each thing that can be spawned. There's a big chart in that pdf.

It's definitely a project not to be taken lightly, and I think it's best to have a plan. Common items near the central areas where your sims go a lot, uncommon ones in more remote parks, and really rare ones hidden off-lot around the map or near "secret" locations, mines, tombs etc.

If you have WA, you get to decide whether you wanna be a lil cheaty and put exotic fish and bugs in your home hood... a bit cheaty cause it means your sims won't have to travel to get em... still, I'll definitely be doing some of that And relics!