You should definitely learn pinyin and the tones (four and the neutral tone) at the beginning, but I would suggest learning these while learning vocabulary and grammar.
It won't be long before you come across all the tones, so that is something you should get used to very early on, but as for the pinyin, I would learn as you go and then cover the rest of the pinyin a bit later on.
If you want any help starting to learn Chinese, I have a free online video course and Skype group, so contact me if you are interested.