This sale goes live tomorrow @ Target. Decent price for most of these, some will likely be cheaper around Black Friday.
Also, the joycon controllers will drift eventually (register movement with no input). There are things you can do to extend the life, but they will get worse. Thankfully Nintendo still offers free repairs, it takes a couple weeks.
Get on a family plan with NES Online, at least the base package. 100+ NES/SNES games on the go and you can play other games (like Mario Kart) online. The expansion is quite a bit more expensive and adds N64, Genesis, game trials and free DLC access.
Once on NES Online, download the free games like Tetris 99. This is one of my favorite games this gen.
Get a large memory card, especially if you're going to buy a lot of digital games. I used to say 128gb minimum, but with the size of required downloads and price of cards now I'd say go 200gb min. My 256 is full and I buy physical when possible. I've had to start deleting games until I can get a 512.
Glass screen protector is a must and should be done asap. Also get a cheap carrying case that has good reviews and holds some games, smaller the better if traveling. Amazon should have both for $10-15 total.
There are so many great cheap indie games, and they go on sale regularly for sometimes over 90% off. Every week there are sales and many great games get steep discounts. Nearly every game has been on sale, so with a little patience you can amass a great digital collection for relatively cheap. Just do a little research before buying as there is a TON of trash in the eShop, and one man's trash is another's treasure. I've only done it once, but there are ways to buy eshop games from other countries (I see Argentina a lot). You can get even better deals doing this, but I'm fine supporting the developers and not dealing with the hassle. Also everything is region free, digital or physical.
There are great collections that can be had cheap as well. Contra, Castlevania, Mega Man, etc all go on sale for $5-10.