I will been in the ILF minority with this opinion, but I've not had good experience with pedals being used with synths or drum machines. Decent results for live use, especially if using an amp, but I notice the top end getting chopped off or cut pretty substantially. For instance, Pretty Years was easily my favorite pedal for guitar. I even loved how it blew up the volca beats particularly (which isn't exactly a boutique sound-wise as I'm sure you know). However when using any pedal, be it dirt, reverb, or delay with any of my nicer units, it was certainly a noticeable difference to high end and clarity. Sticking with the Pretty Years example, it just couldn't contend on drum machines, even their individual outs, with the Analog Heat. PY certainly sounded better on guitar and bass though, and probably EP's like Rhodes and Wurlitzers being amped. I think for a lot of full range synths, EQ, HF dampening, and clean blends are near essential.
I think there are some pedals that would work, but they would have to have a lot of extended controls. I found delays/reverbs like dd3, dd7, canyon, carbon copy, boss RV's, rrr, etc, you know any standard 4-5 control units just weren't working for me. I grew to prefer rack units, even those considered shitty like DEP-5, and early SPX's and some alesis units for the additional ability to shape it around the synth tones and drum hits.
I'd probably recommend something like a Korg KP3+, which has about 60 stellar programs in it. I really dislike any of its HPF's and all things in it's high frequency range though. It has some great LFO's and synth/drum reverbs and delays. Decent stereo-izing effects, though I'm not sure if it's true stereo or summed mono input
Otherwise I'd really recommend considering a decent rack unit. On the cheap side, TC M-One XL's are a breeze to use and a great introduction to units with multiple I/O routing options and algorithm stacking. Ie can be used as 1 dual stereo effect in series or parallel or as 2 mono effects. These can be found for around $150 used.
Or just go big with eventide dsp, and you'll really not need anymore effects ever, especially if you have any interest in programming. After you get past the fear of 20+ year old digital, it's impossible to find a more powerful and still relevant unit than an Orville for under $2k.
Just to be clear, I'm not saying you can't get good effects with pedals on synths, just that "I" can't seem to. Obviously plenty of other people can