STORY
As you may expect from the synopsis of the series, Rio: Rainbow Gate is not a series that focuses all that much on the story.
The basic premise of the 13 "Gate Cards" and the concept of "Roll Rulers" is... pretty vague. It's certainly explained, but not in all that much detail.
Why are there 13 cards? What happens once someone wins all 13? Are they kept by that person? After all, if a Gate holder has to accept a challenge from another Gate holder, if someone has them all, it should mean that they can keep them until they die.
Are the Roll Ruler powers effective on everyone, or only other Roll Ruler users?
But questions like this aren't really what the series is about.
Though I must say, in fairness to the series, there is actual story development. As the show goes on, I was surprised to find that characters not only had backstories but by the end of the series the tone had shifted to become fairly serious. Maybe a little melodramatic, but certainly more serious than one would expect from watching the first few episodes.
ART
Do you like boobs? If you said yes then do I have a show to recommend to you!
The key focus of this series (at least, as far as I can tell) is the visuals. Well, and the characters too, but the visuals are certainly one of the points at which you'll either love the series for it, or dislike it.
The art direction is very much on the side of fan-service. The main character, Rio, is regularly shows in revealing outfits, along with the rest of the cast. All the women are generously endowed with more than enough jiggles and shots to demonstrate that there's a big focus on the female form. Overall, it does exactly what it sets out to do: it presents a cast of attractive girls to oggle while the plots slowly amps up around them.
SOUND
The voice acting is good. It's nothing spectacular but then it's not bad either. It... does the job. The characters sound like you'd expect. Shout out to Killer Bee's (of Naruto Shippuden) voice actor voicing a large stereotypical American.
There are also a lot of moans, shouts, screams and other lady noises that would maybe make people ask exactly what it is you're watching if you've got the anime playing on speakers, so watch out for that if you plan on watching it around people who do not understand the context.
The music is also serviceable. There are some happy, breezy sounding tracks, there are some intense, dramatic tracks and overall it fits the feeling of the show well. There are no standout OST tracks that I noticed, though in the final episode it did sound like they used a track from Naruto Shippuden (one of the Akatsuki's themes) which was a little odd. Maybe I was mistaken, but it sounded very similar...
The opening and ending songs are also, as you'd expect, pretty sugary, happy and overall sound like, well, generic J-Pop. The ending theme is certainly catchy and is almost too happy, but overall both fit perfectly within the show, adding to the "looks before substance" theme the anime goes for.
CHARACTER
As previously mentioned, the characters in Rio: Rainbow Gate do have some depth. Well, the main character does, along with one or two others. The series does focus quite heavily on Rio's past, and her links to Rina and Rio's mother, Risa (Yes, her name is Risa, it's not a mistranslation of Lisa, as she is known as "Double R" due to her first and last name starting with R).
The rest of the cast are fairly one dimensional in terms of personality and character, with traits such as "The clumsy one", "The younger sister who copies her older sister's last few words of a sentence" and "The robot girl with tan lines (How does a robot get tan lines?)". Though, as with many other things in this series, that's fine. Depth and intricacies are not two things Rio: Rainbow Gate aims to deal with in terms of plot or characters.
ENJOYMENT
Now this... THIS is the category where Rio: Rianbow Gate shines!
The anime is set at a casino resort, where having a good time is the top priority. And this anime has the same attitude.
It's not about telling an engaging story. It's not about memorable characters. It's not about a moving soundtrack, it's about fun and enjoyment.
In this sense, it actually feels a little like a trip to a resort/casino: You go there to have fun. You may not remember too many details. You may not have your life changed. But you'll more than likely have fun while you're there.
Personally speaking, this was a fun anime to simply unwind to. Put it on and just zone out, watch the pretty girls and the bright colours (which, by the way, are everywhere. It's always sunny in this anime. Unless it's night) and just enjoy being in a world where people have superpowers that change their odds at games of chance.
OVERALL
Overall this anime has a bit of a niche audience.
It's aimed at people who:
1). Like gambling or games of chance.
2). Like fan service.
and
3). Just want to have a good time and enjoy an easygoing anime.
It's certainly not the only anime to have done this. But what it does, it does well.
If you're looking for something serious, or something memorable, maybe look elsewhere.
Even if you're looking for something with plot progression, this may not be for you.
Honestly, if I had to compare it to something, I'd kinda describe it as a fanservice-heavy, colourful version of Yu-Gi-Oh.
Overall I give it a 7. It was good. It wasn't great. It wasn't bad. It was just fun :)
