As of Eevee Grove, the rarest cards in the game are as follows: It's worth noting that, whenever there are two or three packs in a given expansion, the percentage for each card to be a Gold Crown rare in a God Pack applies only to that specific pack's corresponding Gold Crown rare
There are plenty of other kinds of decks you can build and I cant list all of them, but these archetypes should be enough for you to understand what you can expect from other players and point you in the right direction to get started
As for what the Dragonite card actually does, its main attack deals a pretty impressive 250 damage - very solid for a basic Pokemon card, though your bench does take a hit
Its not as old as some other cards on this list as the expansion premiered in 2003, so itll probably keep going up in value
But for a game like this, you need a card that makes you feel something
Tutors that search for a specific card of a specific type/subtype can be very powerful too in the right deck