The SCX24 uses two different size screws. The most common are M1.4 allen screws. They take a .050” Allen wrench. All of the screws on the kit are this size (in different lengths) except the two screws that hold the motor in. They are 1.5mm. A L wrench is included with the kit but you’re going to find it much easier to use a hex driver.
I have long been a fan of the Integy hex drivers. I have two sets that I have been using for over 10 years and they are still in great shape. You can get cheap hex drivers off ebay and Amazon, but I would recommend paying a little extra for a nice set of hex drivers.
The wheel nuts on the SCX24 are 4mm nuts. 4mm nut drivers don’t seem to be as common. I bought one of the cheap ebay sets (yes, I know I recommend against that…) and it’s working okay, but I’m on the hunt for something better.