The one accessory that I've been using for years is a Logitech mini mouse. I've got to use an USB-C adapter for it. I almost always use my laptop in my lap on my lazyboy so the mini mouse sits on the arm of the chair. I love it. By wife thinks it's stupid. I can certainly use the trackpad but i find the mini mouse much easier.
https://www.amazon.com/gp/product/B008RMY4JQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
I don't ever get Apple Care. I buy my computers with a credit card that doubles the warranty. So, they're covered for 2 years. I've never had a Mac break but if it did happen after the 2 years I'd rather sell the old one for parts and buy a new one to get current technology. Over the years my wife and I have owned a dozen Apple laptops. We've never replaced one that was less than about 7 years old and we've always sold the old one, still working. So not buying Apple Care has saved us a ton. We are careful with our computers so I'm not particularly worried about dropping them. And we live in a low crime area so I'm not particularly worried about them being stolen.