Pedal recommendations

Hey all!

I just have a new Zoom G1ON multi effects pedal which at any given time can do any combination of five, of a couple hundred pedal effects. (It also has a rhythm section and a looper.)

I know that there are hundreds of guitar pedals that are almost or completely useless with the theremin and I would like to skip over those.

So I would like your recommendations for which pedal effectss you like the best, that I should start with.  

Thanks in advance.

Hi, welcome Daniel,

most useful effects for theremin would be delays and reverbs, of which the multi-effect pedal probably has several types (tape echo, analog delay, spring/room/plate/hall reverb), and modulated effects like chorus, flanger, phaser, rotary speaker simulation can have their place, 2 or 3 wah effects set to different bands can simulate vocal like formants (vowel sounds), while a filtron/envelope filter can make the timbre variable with volume.
Fuzz/distortion effects can also be used to change the timbre/wavform, and can also compress the dynamics, so you could get a snappier attack, but at the cost of a reduced dynamic range. Octaver and pitch shifting can be used to extend the range down or up or to add fulness/harmonics or a tone at some interval with the theremin's tone.
A looper function is great, to record something to practice over, or to create something layered/polyphonic.
Filters (wah or equalizer) can be useful, also to use in front of and after a fuzz/distortion. When chaining several effects, the general guideline is filters (EQ/Wah) and fuzz/distortion first, then pitch shifting and modulated effects, and reverb and/or delay last in the chain.
It's often a good idea to use more dramatic/extreme effects sparingly, and otherwise use effects in a subtle way, on the border of being noticeable. But much depends on context and style and what kind of sounds you are after. Spending more time tweaking effects than actually practicing and playing theremin wouild be counterproductive.

Wow! what a thoughtful and comprehensive answer!  Thank you very much, and especially thank you for the suggestions of the sequence of effects.  You have indeed saved me a massive amount of time of playing around with and tweaking effects - time which I desperately need to practice with :-)