If your school doesn't introduce you some method of parametric design, you should consider switching to another one
It hard to answer you as the picture you shown used different method, and in houdini most of the time for achieving one goal, multiple roads exist. Just do not burn the steps many
Grass hoper is also a good option if you are not afraid of its interface. There are plenty of discussion posted here, and paper on the web to read, start with a basic challenge, experiment by yourself and be patient...
Solver, volume sculpting , L_sys, algorithm like Differential growth, DLA, GrayScott Reaction-diffusion, Space colonization, Fibonacci sequence , Implicit surface, Phyllotaxis , shortest path and voroinoid patern, recursion and fractal subd( Hansmeyer ), here few examples of names you should be familiar with, google then, that's not about houdini but they will help you
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Vincent Thomas (VFX and Art since 1998)
Senior Env and Lighting artist & Houdini generalist & Creative Concepts
http://fr.linkedin.com/in/vincentthomas