It's Space Time!

The first Kamen Rider show that I watched and the one that I'd most highly recommend to newer fans looking for a fun, yet intricate, ride through the franchise. All of the characters are established very quickly and utilized very well throughout the story. It's one of the few Kamen Rider shows that makes active use of the girls all throughout. It also moves fairly quickly, with a two-episode format that allows for more decompressed storytelling to sneak up on you.