In my point of view, surveying lammps examples could be quite useful. You can find them in the directory you have installed lammps.
There are some simple examples. You would better start to surveying these examples. Whenever you face a new command, go to the lammps documentation and check that command. You will not need to read all the points about that command. Just ones that you think are around that example.Gradually, you can see that you will read most parts of the common commands.
Besides, I totally recommend that check the lammps workshops. You can find them here:
There is no need to read all the sessions. Just those that you need at this time.
Furthermore, checking tutorial page could be extremely useful:
All in all, I think you should always consider lammps documantation.