How do I get into Getter Robo.
Is there a guide to it like Gundam?
http://getterrobo.blogspot.ca/
1. Getter Robo (Getter Robo Saga Volumes 1 - 2)
2. Getter Robo G (Getter Robo Saga Volume 3)
3. Getter Robo Go (Getter Robo Saga Volumes 4 - 6)
4. Shin Getter Robo (Getter Robo Saga Volume 7)
5. Getter Robo Arc (Getter Robo Saga Volumes 8 - 9)
Then just watch whatever anime you want in whatever order you want. It doesn't matter. They're all adaptations to varying degrees and aren't actually in the same continuity, except the two 70s TV series.
>>349625
Here's a guide to it, but it's basically what >>349660 said. Avoid the 70s TV series unless you want a goofy kids' show. I'd recommend reading the manga before watching the OVAs. You can watch them first but you'll miss out on some references and you won't know who certain characters are supposed to be.