If you're brand new into diving, I'd personally recommend something like a Mares Puck Pro Plus as your first computer.
You can find them occasionally for as little as $150-170 for "new". It will do all you need it to do aside from the air integration.
Why do I recommend this route? Because, a quick check of marketplace will show you that many people don't actually end up getting as much into scuba as they originally thought- if you use a puck pro plus, you get the basic/nitrox calculations you need, and it's easy to read.
If you find scuba is indeed for you, after a few months, look into something like a perdix AI or Teric with AI. You can always use the puck as a backup computer.
Perdix AI has the nice large screen visibility and doesn't use a rechargeable battery that will run down over time.
I personally have the Teric and I like it very much. Sometimes I wish I had the Perdix b/c of the big screen and AA battery.
Why do I think it's better than a Garmin -
It's a dedicated dive computer - that's all Shearwater does, it is fully a quality, reliable computer.
Customer service - This may not seem like a big deal, but watches, etc have batteries and software that run down over time. Shearwater is absolutely the best for customer service - they will even go as far as to send a loaner if you need one.
Transmitter- The Garmin uses an ultrasound based transmitter vs radio used for the Shearwater products.
Why does that matter? - Because the Garmin one makes a high pitched squeal every 2 seconds in your ear - if you have more sensitive high pitched hearing like I do, it's REALLY annoying.
JM2C. Good luck and welcome to diving!