Whats the most effective way of rendering an entity invisible?

what are you using? a tesr or a model? if you use a tesr just put a break statement at the top of your function

I was actually just using RenderingRegistry.registerEntityRenderingHandler to render it like a snowball

Dont render it at all?

 

Im not sure if this answer your question though. Could you explain a bit more what you are looking for? For examle: the potion effect, semi transparant rendering, switching from visible to invisible and back, partial transparant etc.

If i don't render my entity it will render as a while cuboid and i want to get rid of that so i cant see anything.

As i wasnt using do render before can you explain by what you mean leave empty?

doRender(parameters)
{
     // this is an empty method
}

I like to name mine 'RenderNothing'

@SideOnly(Side.CLIENT)
public class RenderNothing extends Render {

public RenderNothing() {}

@Override
public void doRender(Entity entity, double x, double y, double z, float yaw, float partialTick) {}

@Override
protected ResourceLocation getEntityTexture(Entity entity) { return null; }

}

Register this renderer instead of RenderItemSnowball and voilá, nothing renders