I checked wikipedia and according to it there is no scriptual reference of Santoshi Mata in Hindu texts and she just gained popularity after 1960 movie 'Jai Santoshi Maa'. After reading the wiki article it seems as if she is a self created new goddess. Can somebody please explain which hindu texts contains the story of Santoshi Mata and about her other legends ?
Santhoshi Mata has absolutely no basis in Hindu scripture. The earliest mention of her is in a modern-day Hindi pamphlet called the Santhoshi Mata Vrata Katha, which you can read here. In any case, there is absolutely no record of Santhoshi Mata before the 1960's, when her first five temples were stablished. Here's what this journal paper says:
Art historian Michael Brand traced the history of the goddess’ worship to the early 1960s, when five temples to Santoshi Ma were dedicated at widely-separated sites in northern India.
Also, these temples were not originally Santhoshi Mata; rather they were temples to other goddesses which were converted to Santhoshi Mata temples. Here's what this book says about the Jodhpur Santhoshi Mata temple:
In fact, although a temple to her existed in Jodhpur, Rajasthan, she had evidently not been known very long under that name or in that form even there. Before 1967 the temple now dedicated to her had belonged to a goddess called Lal Sagar ki Mata, "The Mother of the Red Lake," near whose banks it stands, and the characteristics of the earlier goddess diverged in important respects from those of Santhoshi Ma. Most significantly, Lal Sagar ki Mata was a carnivore, to whom goats and other animals were periodically sacrificed, whereas Santhoshi Ma is a vegetarian, with chickpeas and unrefined sugar at the center of her diet.
In any case, Santhoshi Mata was popularized by the 1975 movie Jai Santhoshi Maa, which also introduced the notion that Santhoshi Maa is Ganesha's daughter, something that's not even mentioned in the Santhoshi Mata Vrata Katha. For the record, the only children of Ganesha mentioned in Hindu scripture are his sons Shubha and Labha, there's no reference to him having a daughter.
This is a clear indication that although authentic scriptures are available but few original scriptures having more detailed description of God's family might have possibly undergone irreparable loss due to - foreign invaders OR natural calamities over the time. That's why, learned persons only recommend understanding, reading mainly SRIMAD BHAGWAD GITA, as it's the essence of all other Scriptures.
In BHAGWAD GITA, Krishna doesn't mention any Goddess name at all, he simply mentioned once that-
Among women I am fame, fortune, speech, memory, intelligence, faithfulness and patience.
मृत्युः सर्वहरश्चाहमुद्भवश्च भविष्यताम्।
कीर्तिः श्रीर्वाक्च नारीणां स्मृतिर्मेधा धृतिः क्षमा।।10.34।।
I am the Death that carries away all and also the Birth of all that are to be born; among women, I am the Fame, Fortune, Speech, Memory, Wisdom, Constancy and Patience.
Here, women denotes-- DEVI MAA
Here, Patience-- denotes 'Santosh'- one of the qualities MAA SANTOSHI bestows on her devotees. Other Goddess too can be observed in the above verse--
Speech- bestowed by MAA SARASWATI
Fortune- bestowed by MAA LAKSHMI
Fame(power,status)- bestowed by MAA KALIKA