Put a VU meter on each channel and figure out a way to control your gain at the beginning of each track. You can adjust the incoming gain with a plugin or use the gain control that's built into the track. Then, adjust your gain so the highest peak hits around 0 volume units. After you have each audio track's peak hitting around 0 volume units, make sure to adjust every sound effect output volume so that you peak around 0 volume units after each audio effect in your chain. Essentially, you want to ensure that you are coming into the track and every plugin in your chain at the same level. When you're done, you should have a meter on every one of your audio clips reading 0 volume units. This means that all your tracks will have the same signal strength, and you can use your faders to mix and adjust levels accordingly.