I’d recommend Wowhead over Icyveins personally. Wowhead has a comprehensive guide on how to earn the sparks with all the sources and catchup methods. One thing that is a recent addition and is missing from that article is you can buy half a spark from Evantkis in Valdrakken next to the Great Vault. He sells it for 6 Aspect Tokens of Merit, which you can earn by filling 3 of your vault slots in one week.
I do agree the game is really dense and not the most new player friendly. If you are interested, I would recommend trying to find a guild or community that are new player friendly. If you need a place to start, maybe try here: New Player Friendly Guilds Check In Here!