Read the below post.
If you're wanting to go competitive with this game, odds are that you're wanting to find a team, or consistent group of players, to practice and improve or have fun with. These are a couple places to get started looking, and also thinking about things that will help your team not have glaring...
squidboards.com
That said, I feel the need to warn you. You seem quite religious, if that "pagan" comment is anything to go by. It's worth noting that there's quite a large LGBTQ+ presence in the Splatoon community - which makes sense, a game with characters that constantly shapeshift and adapt with minimal gender constraints (aside from the boring clothing options) is going to attract people.
Not going to assume anything about you, but if you're the type of religious person who cannot tolerate the above, you're going to have a rough time.