For me it started out similarly (having seen LWA but none of the others you listed), and just like you I sometimes found a doujin I liked very much despite not knowing the series. At some point I then, whenever I read a good doujin, checked the author's page for related (same series/pairing) doujin, hoping they had the same quality. That lead to having read multiple doujins of certain pairings, so after getting to know the characters in that way, I checked their pairing page. And after reading multiple doujins I knew if the series was interesting or maybe found other characters I liked.
So I got into it bit by bit, and can't link you to some great doujin that will get you to read all of them. Also it's obviously subjective which setting or pairing will be interesting to you, and I personally think that some works are more reliant on you knowing the source material (half of Touhou and KanColle doujins do nothing for me because I don't know character motivations and relations), while for example Love Live is pretty easy to get into if you find one or two characters you like.
Edit: I found that doujin that were not tagged as yuri but drama/comedy/slice of life/introspection were more reliant on existing knowledge of the series, maybe that helps.
last edited at Oct 1, 2018 4:14PM