My unit has arrived, got one of the pro controllers on sale and waiting on the glass screen protector to hit the door. From those that have been using a bit, what other items should I be looking at or what suggestions to use based on experience? Was going to get a blue joycon set when they were all on sale but that color sold out so I'll wait and see if it happens again.
Some things I've bought (in order) and how much I've used them and/or recommend them:
Pro Controller - I use it every time my Switch is docked, except for Mario, where I opt for split Joy-cons. I've got the Xenoblade one pre-ordered. Highly recommended.
Screen protector - I only bought this for the dock scratching the screen issue some people had. Mine was the official plastic one, and it went on perfectly for me. Don't dock without it!
Glass screen protector - I bought this based on other's recommendations. 2 for $10 on Amazon, but haven't used them since my official one looks so good.
Charging Joy-con grip - The system comes with the non charging grip, so you have to connect the Joy-cons to the system to charge them. With the grip you can charge two at once, however, the Power A Charging Station is probably a better value, but this makes it a hair easier, plus you get a grip.
Joy-con sets - So hard to find initially but I finally got yellows, then ordered reds and blues. I interchange them, without preference except for using the grey ones for handheld. They come with straps so no need to buy the matching colored ones, since they don't actually match anyway apparently.
Joy-con Steering Wheel - After I got a few more Joy-cons, I bought some wheels just cause they are fun. The official ones are well made.
Micro SD card - 32GB is not enough for many games, or some games at all. If you plan on downloading ANYTHING, consider a micro SD card required. 128GB+ recommended.
Power A grip (Red) - Bought this at Wal-mart cause it was only $10. It's clearly not as well made as the official ones, but actually feels pretty good in my hands. I've not used it extensively, though, as I opt for the Pro Controller or a grip that can charge.
Case - My first case came with Zelda BOTW Special Edition, but it's too pretty to be carrying around to be honest, so I opted for a generic one from Best Buy for actual traveling.
That's it for my purchases, but some other considerations:
AC Power Adapter - The Pro Controller and the Charging Grip come with a USB C cable. If you ever intend on traveling with your Switch without the dock, you may need one of these. You can also charge the Switch with a standard USB C cable, but it uses power faster than it charges unless you plug it into higher amp source such as wall outlets with USB ports. My powered USB HUB connected to my PC isn't enough, but YMMV.
Dock - I don't think I'll ever buy an extra dock. Not at $90 anyway. If I ever considered it a need, I'd rather buy another Switch which would come with a dock, since some local co-op games (such as Splatoon 2) require two Switches. Which leads me to my final suggestion:
Another Switch - I'll repeat a previous post of mine and make this case again. The $300 price point when compared to the accessories you may consider buying anyway is ridiculously low. Buy a grey one and a Neon one, and buy a Neon (Red/Blue) Joy-con set.
You're already invested in one Switch and all that comes with it, so for another $380 you get the following extras:
-2 Joy-con sets ($160)
-Grip ($15)
-Another dock ($90) (that includes an AC USB C power cable ($30))
If you're considering buying these accessories anyway, they'll total you $265. So you get an extra Switch (again, required for some co-op/multiplayer games), for only $115!
Of course this precludes any unforeseen sale or accessory price drops in the future, but it's worth considering if you're interested.