Can you please tell me if when I`m praying it makes any difference if I read from the siddur or if I don`t look and do it by heart?
There are two distinct questions here: One question is to the necessity of using a prayerbook, the other about the actual pronunciation of the words.
Generally speaking it is certainly preferable to pray from a prayerbook. It prevents mistakes as well as the fact that we are taught that seeing the letters themselves is spiritually beneficial. The only possible exception would be during the Amidah when there is a difference of opinion. Since one should be specially careful not to become distracted then, it is perhaps preferable to pray with one’s eyes closed, even though that means forgoing the prayerbook. Others maintain that using the prayerbook is so vital, that one should risk the distractions that could result from having his eyes open.
As far as the moving of the lips is concerned, that is mandatory. One must always pray loud enough so that he himself can hear his own prayers.