[Nonfractal]

...but it looks fun! How do I dip my toe into the water? 

If you have only ever used RTR cars, the first step should be to buy a white kit from a major manufacturer. 
You acquire some basic assembly, paint and decal skills that way.

Second step is customising that white kit. Better motor, optimised gears, lighter axles, lightweight interior etc.

Third step maybe should be to buy parts separately for a common model to  create a car exactly to your own specification.
My first "from parts" build was an NSR Mosler. 
Pre coloured-lightweight body, one of the chassis options  one of the pod options etc.
You get to select screws, axles, motor, gears, suspension, guide, wheels, tyres etc. ( Not necessarily from the same manufacturer)  and pull the whole thing into a working racer. 
This "from parts" build extends your component selection and assembly skills. 

Maybe as a 4th step, try a generic chassis like the slot-IT HRS2.
Pick up an old cheap body from a swap meet and try to make a competitive HRS2 based racer. 

Go slowly. Pick up the skills and you'll eventually be thinking about buying your own 3d printer or heading toward that place where you'll be carving and moulding your own bodies

AlanW