Welcome to the forum! I suggest you start here:
The first questions you should answer are:
- Do you want to spend time and money (on tools / spare parts) building a board, or buy one that’s already complete?
- What type of board do you want? An urban carver on pneumatic wheels to use no matter the weather or road, or a smaller, cheaper board on urethane wheels that’s easier to carry around, but might not replace your car?
- Once you know what are your goals, if you aren’t 100% set on building it yourself, check what’s already available for purchase. Brands like Hoyt, Metroboard, Lacroix, Flux, Bioboards, etc. are ones we easily recommend on here because of the quality and serviceability of their boards.
- If none of those match your budget / needs, you can talk to one of the professional board builders on this forum (@longhairedboy comes first to mind, I’m blanking on the others at the moment
)
or you can build it yourself!
5) If building yourself, you should first read everything there is to know on this forum (basics about gear ratios, electronics, soldering, etc.), and then pick your parts in this order:
- helmet (and other protective gear, I recommend gloves as a must)
- deck
- enclosure
- drivetrain
- battery
- ESC
- remote
Reason being, that picking parts in a different order may mean you never find a compatible deck / enclosure to house your other parts / be compatible with your drivetrain 
Also: I recommend planning a build solely with parts readily available. Waiting over a year for that 1 last part isn’t worth it 
Ask questions here or in the noob question thread once you’ve done your share of reading! And enjoy your stay