Which game of this series is the most newbie friendly and wouldn't be too complicated or confusing for a player with no experience with creature series?

I would recommend starting off with Creatures 1. The game is a bit easier for a first-time player than Creatures 2 and Creatures 3/Docking Station, although each game offers its own mix of simplicity and complexity. C1 is also great for having a more personal bond with your Norns, while they're a little more independent and distant in the later games. It's really up to you, though! Some like to play by being extremely involved, while others step back and let nature take its course unimpeded.

If it helps any, I'm going to be putting together a few C1 videos to show how I start off after a Norn is born and get him or her acquainted with the language. There are lots of sites out there that also offer glimpses into how different people play the Creatures games, which might help you make a decision. I can definitely post some links, if it would help you out!

In any event, good luck deciding! You can't really go wrong when it comes to Creatures!

By the way, there is also Creatures Village to consider. It's geared towards a younger audience and is a lot simpler, though it's quite different from the main titles in the series. Figured I would throw that out there, just in case you're looking for something along those lines! It's somewhat entertaining and fun for older players, too, although I would recommend getting into C1, C2, and/or C3/DS to experience the bulk of what Creatures has to offer.