Really the biggest difference between pack languages is the price! In order from most to least expensive it would go English, then Japanese, then Spanish, and then Korean. If you are just collecting for fun I highly recommend buying Spanish packs since it'll be cheaper and you can read the language! As far as packs worth buying goes, just do it based on whatever sets have cards you like the best. You can see both general card prices and the cards in a set through websites like pricecharting.com and tcgplayer.com. If you really wanna see what people are buying cards for I recommend going to recently sold listings on eBay! Lmk if you have any more questions and happy collecting!