As a hobby shop employee Pokémon comes in many types of packaging but whatever you do don't buy single cards off Amazon or even lots. The number of fakes I have kids bring in that came off Amazon post the holidays is pretty high.
Packs are generally safe and if you want alot of packs elite trainer boxes come with 9 (atleast for the newer sets older ones vary) and booster boxes come with 36.
They come out with a new set every 3 months or so and the newest is surging sparks which is a pretty popular set. I'd be happy to answer any other questions if it helps your holiday shopping.
Alot of boxes go by popularity elite trainer boces tend to be $50-60 bucks but end up being priced higher if popular enough. Same for booster boxes $120+
I recomend tcgplayer.com for card stuff it's a market place like ebay but just for cards. It was so literally the ebay of cards that ebay acquired it in somewhat recent history. Anything from the "scarlet and violet" series of cards are readily available https://m.bulbapedia.bulbagarden.net/wiki/List_of_Pok%C3%A9mon_Trading_Card_Game_expansions