I asked because he said there were parts I can skip, but going all the way to part 4, seems like I'd be skipping way too much
Basically, this is how the guide is set up.
Part 1, covers how to setup menuhax, via way of browserhax, you replace this with your choice of homebrew entry, if you don't have a working browser or are on 10.6 / 10.7.
Part 2, covers the downgrade procedure to 9.2, if on 9.3-11.0 (with 11.0, you also need a hardmod) - If you are below 9.0-9.2, you follow the 9.2.0 update section instead. You are on 9.0, so you can skip this. 9.0-9.2 all work the same.
Part 3, covers setting up your first RedNAND with Luma3DS as your CFW. You can just do the CFW side, if you want to do via way of Luma3DS, and skip the creation steps for the RedNAND. Luma3DS should work fine on a GW EmuNAND.
Part 4, covers the 2.1 downgrade procedure, and at the end of it, you'll be on 2.1
Part 5, continues right where part 4 ended things off, and quickly gets you set up with A9LH by installing A9LH from 2.1, then goes on to returning you back to an updated sysNAND only environment with Luma3DS as the CFW of choice.