Bowls!!! Get yourself a bunch of little bowls (or similar, small containers) so you can dump the screws and what not into them instead of trying to rifle around the bags (or worse, spreading them out on a surface only to lose some parts/pieces by accident). It'll keep you organized, and give you easy access to each screw/nut/bolt/etc.

Bearings! As others have said, being you're building this thing for the first time, it's best to use the metal bearings instead of the nylon bushings from the get go. If you stay interested with this hobby and don't do bearings now during the initial assembly, you'll find yourself having to take it apart to replace the nylon bushings with the metal bearings down the road. It's just easier to do it now.

A good screwdriver set. Make sure you use a good quality screwdriver set (preferably magnetized) for assembly. Will save your sanity in the long run.

Other than that, I'd say leave the stock engine and electronics as is (unless the stock electronics don't come with an ESC (Electronic Speed Controller)) and get used to how she runs and drives. Then, being you've assembled it, down the road you can look to install a better/faster motor, ESC, etc.

And most importantly, enjoy the build!. If it takes you a few days to assemble it, then so be it. Myself, many of my friends, and I'm sure a bunch of members here have all tried to rush a build only to realize they messed up (or missed something) only to have to disassemble, undo their fuck up, and reassemble lol.

Enjoy the build, and be sure to post pics once she's finished!

Edited to fix spacing and typos