ATC

Most of the comments thus far aren’t aware of the differences between a standard ATC, and an ATC Pilot. You can’t go wrong with a grigri or Pilot but the Pilot is the better option for most first devices IMO. Unless you’re gifting it to someone. My recommendation is not as a former Black Diamond rep

I have a Giga Jul and use it as my primary device for gym and outdoor sport climbing. It's super versatile, and can be used with double ropes as well as for rappelling, but if you're not going to be doing that, then your options are more open. I haven't used the Ocun Bow, but it looks to be the same

Black Diamond ATC pilot or mammut smart are my recommend devices if you need an ABD. I use my grigri and Giga Jul all the time but my Pilot is my lead belay device in the gym. It is lighter, more intuitive - especially if you already know a standard tube style device, and smoother than a grigri. All