I'm glad you like it! I actually made my first prototype right before last Christmas so I could play it when my family got together, and people enjoyed it so much I just kept working on it.
As far as gifting goes, I actually didn't know you could get Steam gifts that deliver later, so I'm not entirely sure of the answer, but I assume if they charge you for the game right away it would process the payment then too.
Full disclosure though, only one person needs a copy of the game to run it and play with a group. Everyone joins the game by visiting a website (generally on their phone), similar to how Jackbox games work. So there's no obligation to gift copies, but if you still do I will be quite honored and grateful!
Everyone has their own process, but I think it's fine to just start with a simple idea that's not yet a game, jump in, and experiment around, especially if you're just starting out. I'm not an expert by any means, but I managed to release a small game of my own recently, and all I had at the start was a test where I could knock over a box by throwing a ball. Everything else that eventually became the game were ideas that I had later while playing around and showing it to other people.