something which occured to me lately :
gainers are partly good and partly evil.
After making a few tracks with loads of effects I realized that I had a gainer or two infront of each to rise and lower volume all the time.
because some plugins dont really work with too loud or too quiet samples I suggest you use a gainer as first effect and a gainer as last effect only.
the first gainer is used to kind of normalize the track you want the effects on, because if you have a very quiet sample/instrument there are some effects such as compressors or similar wont do anything, while when using a very loud sample you may get distortion.
so use a gainer first, then some plugin which gives you the peak of the track and adjust the gainer so that the peaks are at about 0db.
then run all the effects you want and finally put a gainer at the end and use that one (and only that one) to set the volume of your track.