I know that wasn't your question but I suppose it might still be relevant.
Me playing in an original band where I got the main compositioning chores I will, by now eventually having build an effects setup that seems to work for most of my ideas, mainly try to compose based on the pedals I already got, however if I come up with something that will require a specific effect to work optimally that is not in my setup I will try to find an effect as closely matching the requirements as possible, and if it doesn't happen to be in my collection already I will buy, sometimes that takes several wrong purchases, since I don't really have any option of trying out a lot of different pedals in my reasonable proximity.
But then again in the musical project that current got my main focus and where I as said play bass and is the one mainly responsible for writing songs I don't really tend to use effects in a way that reasonably could be classified as just subtle flavor if not already an integrated part of my basic always on clean tone, when I use effects for the songs I write for this project they tend to usually play a quite essential role to the composition.
And yes, I actually got 1 pedal in my setup, added fairly recently, that currently is only used for 1 song, though that is likely to change for more songs as time goes on.
I kind of believe I finally have reached a point where I have build up a pedal setup that ought to cover what is to become this projects "sound" and kind of hope it won't be necessary to add additional pedals in the future, but who knows what I will come up with as time goes on, the project is still at a pretty early state where thing are slowly coming together, just recently starting to rehearse with a drummer friend of mine who will mainly just be responsible for coming up with the drums parts, plus a little additional vocals and synth work, though I worked on songs and my setup for the project for over a year by now.
For the sake of context the project I am speaking about is sort of a progressive psychedelic stoner/doom rock bass/vocals and drums/vocals duo.
My basic "clean" tone consist of a parallel (as on mixed with clean signal) compressed signal, really just adding extra punch, snap and bit to my tone, but without really affecting my playing dynamics, an always on 1 octave up effect mixed with clean signal, giving an effect somewhat similar to that of playing an 8 string bass, with pairs of respective bass and octave strings and a low gain grinding kind of overdrive, mixed in parallel with clean signal, adding a bit of grid, some extra snap and bite and enhancing harmonic content of my clean signal.
Additionally following effects are used:
- A high gain, quite raunchy and somewhat fuzz-esque, distortion, consisting of a Rat clone mixed in parallel with a Joyo Orange Juice low gain overdrive staked into a Boss MT-2 Metal Zone distortion
- A high gain octave fuzz delivered by my Behringer SF300 Super Fuzz, mixed in parallel with clean signal
- A phaser with a relatively high feedback and wide sweep setting mixed in parallel with a flanger effect
- A lush chorus effect from a pedal based on the Boss CE-1 circuit with a tremolo stacked into it
- A NUX Tape Core Deluxe delay pedal, which is a digital Roland Space Echo tape delay emulation.
Regarding cover band, though I could not ever picture myself in one, I would properly aim for acquiring any effect that played an essential part for a song, even if it was just 1, whereas if it was just a subtle flavor effect I'd probably see how the song would work out without it, and otherwise just roughly approximate a somewhat similar effect with whatever I could find on one of my digital Zoom multi effects.
) I'll rather add a pedal if I feel that I need it rather than stacking all I got in one pot. 
