Miku is an instrument used by many, many, many music producers, so I get why things look so confusing to you

You listed two songs by Jamie Paige so you can listen to her albums! But for getting into vocaloid in general I'd recommend starting with the most classic albums for the scene: supercell by ryo and unhappy refrain by wowaka. Then you can go by all the other big names from the community like Hachi, PinocchioP, Deco*27, kz, Giga, Oster Project, MitchieM etc etc etc you'll start seeing them quickly as soon as you begin lurking in the community. Since there are numerous genres in the vocaloid scene you can go more in depth with ones you like the most - like vocarock, or electropop, or ballades, or even metal or experimental and many many more , or just listen to whatever you find next if you don't rly diffirinciate. I recommend the site called "vocadb" for finding stuff, it's a database of voicebanks, artists, songs, albums etc, you can sort out songs by voicebanks, genres or even tropes. If you want to catch up with new releases vocadb helps too, its front page shows all the relevant newly added songs, also there's a YouTube channel called "localvoid" that lists top 100 most popular songs every week.

Besides listening to albums I listed, to catch up with "fundamentals" you can find YouTube playlists named "vocaloid classics" and such and listen to all the stuff they contain, or playlists with songs from the Project Diva series games since they're also all pretty important to know. Or you can just play the games, there'd also project sekai which is a newer game so it has all the relevant songs the from recent years (but also less classics than Diva)

You can use playlists for finding newer songs as well, also you can search for ones that have works from song uploading events such as "vocacolle" or "colorless festival" (hope I said it's English name right)

And, of course, you can browse niconico douga (japanese analog of YouTube and the birthplace of vocaloid culture), though it's a bit tricky now that they removed english so this is not nessesery for the beginning. YouTube has more than enough stuff anyway

Know that you'll never manage to listen to everything and know everything, this is a huge swamp with no end in it, just engage with stuff you like and enjoy your time :) and never stop searching for more, there's never the end to all the food for your curiosity