The movies and the specials are not canon in a way, so they shouldn't affect your viewing of the series. I would still recommend watching the full series first then watching the rest, but again you can watch them in the order you want
Sailor Moon Classic
Sailor Moon R
Sailor Moon R Make Up! Special
Sailor Moon R - The Movie
Sailor Moon S
Sailor Moon S - The Movie
Sailor Moon SuperS (first 4 episodes)
Sailor Moon SuperS TV Specials
Sailor Moon SuperS (the rest of the episodes)
Sailor Moon SuperS Ami’s First Love Special
Sailor Moon SuperS - The Movie
If in doubt, look up the air dates/release dates and watch them in order of release.
The films are in their own independent continuity but if you want to watch them in their most logical placement it makes more sense to watch it after Usagi and Mamoru get back together but before the gang heads to the future.
There’s no objectively correct way to watch them. Hell when I rewatch the Optimum dub I watch all 3 between R and S to align with dub production order *shrug*
Just here to acknowledge that the posts by @ChibiBoi and @NJ_ have served as my primary source of knowing what the hell I'm watching and now that I'm on season 5 I don't need to keep lurking this thread