What is the effect of increasing your ram in blender? Especially in the speed of rendering
RAM is mostly about storage amount. More ram will allow you to render more complex & more populated scenes (more objects, more polygons, more textures, etc....).
It will not have a significative impact on render times, unless you have less ram than is needed to handle the complexity of your scene (the more complex the scene the more ram is required) - in which case your system will store on your hard drives, which are way slower.
The important hardwares in render times are the CPU and the GPU.