Here we go, some spoilers but it's not like the story is that unpredictable anyway...

Ep 1 - Sailor Moon is introduced
(Ep 3 - iirc I like this one a lot)
Ep 8 - Sailor Mercury is introduced
(Ep 9 - I think I liked it a lot when I first saw it? Also, more about Ami)
Ep 10 - Sailor Mars appears
Ep 12 & 13 - Jadeite is defeated (also, I like the monster in ep 12. And the girls go on a "date")
Ep 14 - Nephrite appears
(Ep 19 - Love letters and double-gangers. Semi-important and pretty good)
(Ep 21 - Anime studio injokes and the victims of the week are a pair of female friends. Completely plot-irrelevant but a bit cute)
Ep 23-24 Nephrites end. Really good episodes for season 1
Ep 25 - Sailor Jupiter appears
(Ep 28 - not that important, but a sweet victim of the week and some foreshadowing)
(Ep 30 - backstory for Rei)
(Ep 32 - Some Moon backstory and good comedy bits. Tuxedo Umino!)
Ep 33-34 Double episode, Sailor Venus introduced. Important
Ep 35 - Plot-relevant. Zoisite ends
Ep 37 - Very funny ep
(Ep 42 - Sailor V's backstory, bit of a different feel. Good)
Ep 43 - 46 Basically the final, watch the entire bit. It's worth it