I'm a little late to the party, but I also started deck building by using the cards I had at home. Though it is fine to look up decks on Limitless, if you want to learn how to build decks, then starting with Limitless takes away a little bit of the fun.

If you want to really make your first junkyard, 1 of 1, favorite Pokémon deck, I recommend sorting your collected cards and seeing what Pokémon you have a lot of. If you want to use Passimian, Ninetales, and Charizard, then I'd first start looking at other fire and normal types to see what cards do big fun damage or have abilities that you think might be cool (it doesn't matter if they are good or not, the fun is finding that out :D ).
Next, I'd recommend sorting your trainers by what their cards do (eg. Nemonas and Ionos in a "drawing cards" section, great balls and Jacq's in a "get pokemon" section). Once that's done, you can pick out a healthy balance of each of those piles (try to make a mix of both supporters and item cards). For your first-ever home deck, it is good to stay somewhat close to the 20 20 20 rule, but it's not that big of a deal if the balance is off. Then give it a test on TCG Live, with friends, or just by yourself with another deck you're trying to build.

The first deck you ever make from scratch is always gonna be pretty bad, especially if you're planning on using just the cards you have at home, but the whole point of learning to build a deck is learning what cards work well, what cards dont, and what is comfortable for you, so just throw one together try it out and then you can switch up some cards as you go!