Compression
Pre amp
envelope
reverb
octave
distortion
I am not really sure

but I'll try my chances... it's a very good question anyway!
Instinctively I would put the preamp first, as active basses have a preamp already on board, before the signal exits the instrument.
Then, as far I understand, compression works on envelope, while distortion works on instantaneous amplitude. So I would put compression before distortion so that notes which have been balanced in envelope by compression will receive the same amount of distortion. It probably makes little difference in practice but I think theoretically if you distort first, the compressing later might result in notes that are balanced in envelope but may have different degree of distortion.
The octaver adds a (sub)harmonic (another frequency) to each note. Distortion creates harmonics but effectively acts on the signal's instantaneous amplitude. With the octave first, the instantaneous amplitude is not obvious. In order to preserve the (presumably wanted) shape obtained by distortion, I would put the octave after the distortion, where it would add the subharmonic to each harmonic created by the distortion.
Reverb works in the time domain but equivalently emphasizes or deemphasises frequency at specific intervals. In any case its purpose is to recreate the psychoacoustic effect of being in a (typically large) room. So I would put it last in order to work on the already previously created sound.
I am not yet family with how the envelope effect works so I have to skip it, so my choice would be:
Preamp -> compressor -> distortion -> octaver -> reverb
Of course this is only my reasoning as an engineer rather than a musician so in practice it might be completely wrong
