If you want to preserve the gradient as is in your bottom layer, then you can apply a silhouette transfer mode (your toggle now is set to 'normal'). Mess with those, one of them will get you there.
Or you could simply add the mask to your gradient layer. But I'm assuming there is a reason you didn't want that.
Does anything in that comp animate? It doesn't look like it.
From your limited screenshot it's impossible to make any sense of your setup. It seems you are making a mess by using effects that do not generate/ retain transparencies. Much more information is needed.
Turn on the transparency grid to see the transparency. If that doesn't give you what you need then we need a screenshot with all modified properties (press the u key twice) of all layers you are having problems with revealed and the transparency grid on. This is really basic AE. If you are new please start here: Basic AE