Foundation pedals first, of course...
1. Turbo Tuner, gets a completely unadulterated signal for max-tuning accuracy. I'm freq'ish about that.
1a. The Octaver you're planning to get.
2. Submarine, since it is the core tone machine.
2a. Octaver can go here, too, after the Submarine if the Sub's not set too hot.
3. 443 Filter, since that's my preference to have filters/autowahs before dirt. (Though I like my manual-treadle wah post dirt).
Dirt will naturally compress your signal, its the very nature of clipping. So I like to get maximum pop out of the filter, first, by having it react directly to my playing. I like the sound of a traditional wah after dirt.
4. Amptweaker Tight Drive, having the filter spike the dirt can produce some crazy soft and hard distortion depending on how the filter is hitting it. The dirt can also help tame the filter's smaller spikes.
5. Compressore, after dirt because you can set your dirt in such a way as to mildly breakup while playing lightly and then crunch when you dig in hard on the strings. Dynamics, you don't want to kill them all, but Compressore's still after the filter to rein in those huge filter spikes that blasted through the dirt.
6. Ampeg SCR-DI, end of your current chain. The Scrambler will benefit from being hit with a hot signal from your Amptweaker and the Compressore will also help feed the Scrambler a consistent signal — it's not the type of octaver that needs superlative clean signal to track well. It's kind of like a Green Ringer (which Dan Armstrong designed based on the Scrambler). You can also use the Amptweaker and/or Compressore to smack the front end of the Ampeg's dirt section. Smack it hard. It likes it.
More importantly, the Ampeg is at the end of my rendition of your chain because when the magic smoke is released from your Magjellionamp for whatever reason (the singer used it as a beer coaster or whatever), by the time the magic smoke has disappeared you'll already have swapped the XLR cable from the amp's DI to the Ampeg and the only one who'll notice what happened is your FOH sound engineer — you've still got all your effects to play with and they're going to FOH. The audience won't have heard/seen the swap, and neither will your bandmates.
Further to your Octaver hunt:
Listen to (lots of) demos of analog and digital octavers. Decide what you want from your octaver (for example monophonic synth emulation, or do you need polyphonic capabilities that only digital can provide?) I like playing chords and I need a clean octave up *(analog octave up is always a bit dirty), I have a Mooer Tender Octaver (POG clon-ish in a smaller box saves pedalboard real-estate). I also have an M5 MFX that can emulate a variety of other (monophonic) octavers. You may find you use your octaver a lot, or barely at all – depends on what kind of music you mostly play, so that may factor in on your decision-making process. If you're in a funk band, for example, you'll be able to use the octaver a lot, maintain your "buy the best, buy it once" mantra. Otherwise, if you hardly ever use it, there are some fun cheap octavers out there (like the Mooer).
For a great monophonic octaver, try to snag a Broughton Broughtave.
One last suggestion: consider more modulation.
Southampton Utility Knife and/or a Dr Scientist BitQuest get you several good sounding effects in one small box. Yes, vermillion there is a Santa-sounds MFX...
So, as you can see everybody has there reasons for putting stuff in a specific order: like auto-filterwah pre/post dirt — there's no wrong way to do pedal order so you've got nothing to lose.
Oh, one last thing. Some effects can do line-level (and be placed in your amp's effects loop), but most pedals are instrument-level only (and will sound really truly horrible in your amp's line-level effects loop — unless your amp can accept instrument-level signals)...
So many variables.
Great to have 'm.