>>23451367 (OP)
I'll tell you how I got into Mazinger and maybe it will help. There's not really much to 'get' since every adaption is different in some way, but you always see the same events cropping up and the same characters maybe with a slightly different world background or order of events.
OG Anime adaptions I found rough, something you can watch every once in a while but don't try to binge it. The original manga's for Z and Great are not too long compared to something like Getter and once you've read both of them then you are all set for watching or reading whatever else you want so I would start with those.
Animation-wise the easiest entry is Shin Mazinger Z: The Impact
Be warned treat the first episode like the start of Baccano. It is normal to not know wtf is going on since its showing scenes outside chronological order, just a lot of frontloaded action and should be rewatched after the end.
The early episodes also suffer from repeated scenes and flashbacks but it gets better as it goes along.
After that the other notable stuff would be
>Mazinkaiser
OVA taking place after Great, but acts like most events of Z never happened so most episodes are just Z-era plots that are somehow only now happening. What the hell were Dr. Hell and co. even doing in this continuities versions of Z and Great then?
Overall wasn't a fan of it. The titular mech is great, Boss gets a good moment, there's a fanservice episode but not really much else to write home about
>Shin Mazinger Zero
>Shin Mazinger Zero vs. Great General of Darkness
These two manga series go crazy and end with a love letter to the whole Super Robot genre, really worth going through. Its got an almost Getter Armageddon start with classic Nagai gore and not knowing whats going on. Also incredibly horny at times.
>Mazinger Infinity
A solid meh movie. Lots of long colourful CGI fights and a future look at Koji but something about the whole thing just didn't click