Be sure to find a monitor that will actually take advantage of whatever you decide to build. Whether you’re thinking of making upgrades to an existing PC or building a whole new one this is something a lot of people forget to consider while making part lists/budgeting.
Anything above 16GB of RAM is pretty excessive if you just plan on gaming, even 16GB is more than you need. Bulk up on storage so you never have to worry about it again. A 2tb HDD will give you peace of mind and last ages. It’s pretty easy to find parts with matching colors if you’re into your PC looking cool (if you’re gonna pay a bunch you might as well have it be nice to look at!) There’s a lot of accessories/bracelets for grounding, keeping you from transferring static electricity to your parts and potentially damaging them, but they’re not necessary honestly. Just don’t build on carpet and try to ground yourself on other metal objects during the building process.
In terms of additional tools and stuff you don’t need too much. A screwdriver for case screws, and a toothpick helps if you accidentally bend any pins out of place. The CPU cooler I have came with a tube of decent thermal paste but it’s nice to have some extra handy. I’m sure other people with more experience can chime in here with plenty of stuff too. Enjoy building, hope it comes together great for you if/when you decide to pull the trigger and start!