First of all, know that you shouldn't layer sounds unless you have a specific role for each layer. Think it through and see if you can identify each synths role in creating the lead sound.
Second, check the volumes of your synths within the individual synth. If its high a volume, it won't matter at what level the Insert volume is currently at.
I cannot remember who said it, but the saying goes that 80% of mixing is adjusting volumes. Make sure you are aware as you produce of the elements that need to stand out the most, and then continue on by adjusting the volumes based off that element.
Feel free to message me if you have any more questions.