If you do not have any experiance regarding modular syths and how to build them by yourself, my recomendation would be to start virtual modular.
Stop. Dont complain. Read ahead!
If you go to Clavia Nords homepage, you will find a virtual modular synth demoing their (meanwhile dis-continued)hardware-Synthesizer named "G2".
This demo is for FREE and can be found here:
http://www.nordkeyboards.com/downloads/legacy/nord-modular-g2
If you download it and read the manual, you get an idea of how it is going to be to work with a real modular.
If you start working with it, and you start to wonder why you dont hear anything, its way better to learn this and other Basics in the virtual environment.
This way you avoide the usual traps when starting with modular synthesis from scratch, which is buying modules you realise later on you did not need at all.
Within this virtual modular synth you get hundreds of modules (for free) which you can pull and wire up.
You get voices, oscillators, amps, modulators, input-, output modules, effects and complete synth-voices of course too.
If you start this way and collect your own knowledge from hands on experiance (no matter that its gathered virtually), you will avoide disapointments.
I started this way years ago, and it served me right.
PS: if you start with a Mother32, you have to realise that it may have CV-ins and CV-outs on this synth, but you have to do something with this CVs. Just having the ins and outs does not help you if you do not use this signals or alter/vary this signals somewhere and send them back or somewhere else where they are used for something.
A single Mother32 is alone just a normal synth with one voice.
In regards of modular synthesis, buying a Mother32, its like buying a trailer. You can move in and live inside. But if you want more and move around, you will have to buy an "additional" car thats able to pull it somewhere else.
If you allways want to stay at the same place a Mother32 is fine. If you want to move somewhere else you need to dive deeper into the topic to find out what car you are going to need in the future.
"I want to buy a car" - "Which one, Sir?" - "A blue one" ... is not going to be help you find the correct one.
Try to discover what you want - by learning.
Then, - go shopping!