Pokemon cards!! - needs advice

Well, the basic rules of the TCG are not that difficult, but always try to memorize them because sometimes you can lose due to a small mistake that you don't even notice. And if you're going to participate in competitions, always be aware of which model is in rotation for the year. In case you don't know, at the beginning of each year (this year's hasn't come out yet, if I'm not mistaken), the Pokemon Company rotates some types of cards so that some old models can't be used. So always pay attention to that. For example, last year, only cards with the letters F, G, and H could be used, but some informal championships don't care much about that. And about the deck, if you're in doubt about building one, you can buy a ready-made one. I highly recommend the Charizard and Gardevoir ones, both of which are monotype. 

If you're only bothered about collecting id reccomend starting wth some of the smaller collections like obsidian flames because going after the main sets like prismatic eveolutions can be really expensive atm.

I've been seen a lot of people having a hard time finding physical cards so I personally recommend trying out TCG Pocket if you're looking to battle. It's a lot easier to start on there since you don't need to buy physical packs to get a good chunk of cards, and there's rental decks you can get to use in solo matches against the computer to help you understand the basics of battling. Live does have some decks you can use at the start too, but the primary way of getting new cards is using the codes from physical products, since it uses the same exact cards.

The rules are a little bit different compared to what's done with physical cards/TCG Live, since it's meant to be a quicker battling experience, but it shouldn't be too difficult to pick up the rules for the physical tcg/live game once you get the hang of it and can actually get cards to play with.

I think the biggest change between how battling in Pocket works compared to physical/Live is how the energy system works and deck size. Pocket has a 20 card deck and energy is just generated from a pool, meanwhile physical/Live has a 60 card deck and energy cards are pulled from the deck rather than being generated by the game.

If you're looking into just collecting physical cards then be patient and don't give scalpers money. If language isn't an issue and you just want the art, I've heard you can usually find cheaper prices for non-English cards. Collect what you want and have fun with it, and try not to focus on getting the most expensive cards if they don't interest you.