Effects pedals: How much amplification?

[Lectroid]

When building a guitar effects circuit, how much can the effect box amplify the guitar signal without overdriving the amp.?  If I have a 100mV input signal to the effect, does its output signal voltage need to stay in that same ballpark? 

I know many pedals provide some boost, but how much would be too much?

[uki]

Interesting question! I never though about it. The variables can be diverse to actually say for certain. It depends on the instrument, pedal(s) and amplifier type, the settings on the whole rig, and so forth. But much of all of it goes by ear !