"How can I start Tantra Sadhana?" and "What are the scriptures I need to study in order to gain a thorough knowledge of Tantras?" are two separate questions unrelated to each other.
One can not practice Tantra without Guru Diksha (initiation).
As Lord Shiva says in the following verse that all practices that Tantras advocate, like Yoga, Dhyana, Puja, Japa etc are useless if the person is Adikshata (uninitiated).
AdikshitA ye kurvanti japapujAdikAh kriyAha |
Na phalanti priye
teshAm shilAyAmupta vijavat ||
[Lord Shiva says to Sri Devi] Whatever a person, who is not initiated
(adikshita), does, whether it is PujA (worship) or Japa (chanting) or
any other religious acts, prove abortive, just like seeds sown on
stones do not grow into plants.
KulArnava Tantram 14.96
Also, as stated in the following verse, knowledge of Tantras, Mantras are useful only if directly learned from the Guru's mouth.
PAramparyA AgamAmnAyAm mantrAchArAdikam priye |
mukhAllabdham saphalam syAnna chAnyathA ||
ParamaparA (lineage/tradition), Agamas (Tantras), AmnAya, Mantras,
AchAra (conducts) are all fruitful if obtained from the Guru's mouth ( i.e
directly learned from a personal living Guru), and otherwise not.
KulArnava Tantram 11.46.
So, in short, for practicing the discipline of Tantra, one needs an initiation from a Guru.
This is the way it should be done and that is the way is done. If you see Sri RAmakrishna Paramahamsa's life, he practiced Tantra under his female Guru Sri Bhairavi after being duly initiated by her.
Another great Tantra SAdhaka, BAmAkhepa was similarly initiated into Tantric SAdhana by his Guru KailAspati BAbA.
Regarding the Tantric scriptures which you want to read to gain knowledge, it is a huge syllabus. How many of them will you be able to read? There are 192 KrAntA Tantras only. Plus there are many more of them.
I am giving the names of few Tantrik scriptures here taken from this PDF:
Mahesvara Tantra says, tvaya proktani tantrani catuhsastimitani bhoh
Oh Lord! Sixty four (64) Tantras were revealed by you.
Tantra also says that the number of Tantra is fourteen thousands
(14,000) . - sapta sapta sahasrani samkhyatani manisibhih |
So, as you can see, some scriptures say there are as many as 14,000 Tantras in all.
The List of few Shaiva Tantras are:
The eighteen Agamas16 which are also called Saiva Tantras, are the
l.Vijaya 2. Nihisvasa 3.Svambhuva, 4. Vatula, 5. Virabhadra,
6.Raurava. Makuta, 8.Viresa, 9. Candrahasa, lO.Jnana, 11. Mukhabimba, 12. Prodgita, 13 Lalita. I Siddha, 15. Santana, 16. Sarvodgita, 17. Kirana, 18.Paramesvara. Nihsvasa Tantra itself mentions these eighteen
Agamas as constituting the Sivasastra transmitted by Rudra. It also
mentions ten more Saiva Tantras transmitted by Sadasiva. They are as
- Kamika 2.Yogada 3.Divya 4. Karana 5. Ajita 6. Dipta 7. Suksma S.Sahas
9.Asta 10. Amsubhed
Then, there are the YAmala Tantras which are mentioned in the list given in the Srikantha SamhitA:
The principal Yamalas are eight in number. They are -
- Rudra 2.Kanda (Skanda) 3. Brahma 4.Visnu 5.Yama 6.Vayu 7. kuvc .
8.1ndra. Two other old texts belong to the Yamala group. They are- I. Pingalamata 2. Jayadratha Yamala.
Srikanthasamhita mentions the following names -
(a) BHAIRAVA TANTRA
II. Svacchanda Tantra 2.Bhairava 3.Canda 4.Krodha 5. Unmatta Bhairava
Asitanga Bhairava 7. Mahocchusma 8. Kapalisa.
(b) YAMALA TANTRA
- Brahma Yamala 10. Visnu Yamala 11. Svacchanda Yamala 12.Ruru Yamal, 13(?) 14. Atharvana 15. Rudra 16.VetaIa.
(c) MATA TANTRA
- Rakta 18.Lampata 19. Rasmimata 20.Mata 21. Calika 22.Pingala 2 Utphulla 24.Visvadya.
(d) MANGALA TANTRA
- Picu Bhairavi 26. Tantra Bhairavi 27. Tara 28. Brahmi Kala 29.Vijaya Candra 31 Mangala 32. Sarvamangala.
- Mantra cakra 34. Varna cakra 35.Sakti cakra 36. Kala cakra 37. Bindu cakra
- Nada cakra 39.Guhya cakra 40. Kha cakra.
(!) BAHURU PASTAKA
- Andhaka 42. Rurubheda 43. Aja 44. Mula 45.Varnamanta or Varna Kanth
- Vidanga 47. Matradana 48.Jvalina.
- Bhairavi 50. Citrika 51. Hainsa 52. Kadambika 53. Hrllekha 5 Candralekha 55. Vidyullekha 56. Vidyumata.
(h) SIKHA TANTRA
- Bhairavi 58. Vina 59.Vinamani 60. Sammoha61. Damara 62. Atharvaka 6 Kabandha 64. Sirascheda.
etc, etc ...
Then comes the list of DAmara Tantras which contain magical rites:
Similarly the Damara which ordinarily means charm magic and miracle
has also its own six branches.
- The Yogadamara of 23,533 verses.
- The Shivadamara of 11007 verses.
- The Durgadamara of 11503 verses.
- The Saraswatdamara of 9905 verses.
- The Brahmadamara of 7105 verses.
- The Gandharvadamara --
This branch mainly deals with magic and science and has 60060 verses.
There is not a single way of life, system of thought, discipline and
code of conduct, creed, cult, faith of religion which does not come
under purview of the Tantrashastra.
Now, as said already, Tantras have also been classified into the three zones with having the names Vishnu KrAntA, Ashva KrAntA and Ratha KrAntA, with each of these groups assigned with 64 Tantras each. So, there are in all 192 KrAntA Tantras only. Moreover, there more than hundreds of Upatantras.
- Uttara 2. Kali 3. Kularnava 4. Kulaprakasa 5. Kriyasara 6. Kubjika Kalivilasa 8. Kuloddisa 9. Kulamrta 10. Kumari ll.Kamadhenu 12.
Kamakhya I Kulacudamani 14. Ganesa-vimarsini 15. Gavaksa 16.Gandharva
- Camunda I Jnanarnava 19. Tantraraja 20.Tantrantara 21.Devyagama 22.Devi 23. Devapraka-
24.Navaratnesvara 25. Nibandha 26. Nitya 27. Nila 28. Niruttara 29. Phetkari, Brahmayamala 31. BrhatsrTkrama 32. Bhavacudamani 33.
Bhutadamara 34. Bhairava 35. Bhairavi 36. Matsyasukta 37.Mundamala
38.Malini 39.MahakaIa 40. Malini-vijaya
- Maya Tantra 42 Yamala 43.Yantra-ciniamani 44.Yogin1hrdaya 45. Yogini Tantra
- Yoni 47. Radha Tantra 48. Rudrayamala 49. Lalita Tantra 50.Visvasara 51. Varah
- Visuddhesvara 53. Sri Krama 54. Sivagama 55. Sukumudini 56.Siddhesvara 57 Siddhasara 58. Siddhasarasvata 59. Siddhiyamala 60.Sanatkumara 6 1. Samayacara 62 Sammohana 63. Svatantra 64. Hamsa Mahesvara
- Uddama-mahesvara 2.Kriyasara 3.Kala 4. Kamini 5. Kamukesvara t Kamaratna 7. Kuranja 8. Gayatri 9. Gurvarcana 10. Gopya 11.Gopi
12.Gauri 13 Gupta.
- Guptasara 15. Guptadiksa 16.Gopalilamrta !7.Cudamani 18.Cina Tantra i‘; Jayaradhamadhava Tantra 20. Tattva-cinta-mani 21.
Tattva-sara 22. Tiksna 2 DhumavatT 24. Brhatsara 25. Brhat-cina 26.
Brhat-todala 27. Brhannirvana 28. Brhat Kangkalini 29. Brhat-yogini
- Bindu Tantra 31. Brhanmoksa 32, Brhanmaiin
33.Bindu 34. Brahmanda 35. Bhutalipi 36. Bhuta-suddhi 37. Bhutesvari 38. Bherund
- Bhuvanesvari 40. Mahavira 41. Mantra-cinta-mani 42. Mahaniruttara 43. Mohana Mohini 45. Madguli 46.Maya 47. Mahamaiini 48. Moksa 49. Mahamaya 50 Mahayogini 51..Yogarpava 52. Yantracuda 53. Yoga Tantra 54.
Lilavati Visuddhesvara 56. Vidyullata 57. Varnasara 58. Sivarcana
59.Savara60.Sulini 61. Siva Tantra 62. Siddha Tantra 63. Saratsara 64. Samirana
- Akasa-bhairava 2. Acaracara 3. Indrajala 4.Uddama-mahesvara 5. Bkajaia
- Kahgkalamalini 7. Krkalasadipika 8. Karala-bhairava 9. Kaivalya 10. Kulasadbhavi 11. Krtisara 12. Kalabhairava 13. Kalottama 14. Garuda
15.Cinmaya l6.C'inacar;> l7.Chayariila 18. Jnanabhairava 19. Deva^amara 20. Daksinamurti 21. Navaratnesvar;
- Nagaijuna 23. Naradiya 24. Purascarana-candrika 25. Purascarana-rasoliasa 26 PancadasF 27. Picchila 28. Prapancasara 29.
Paramesvara 30.Brhad-gautamiva 31 Balavilasa 32. Brhad-yoni 33.
Brahma-jala 34. Bijacintamani 35.Bhuta-bhairava 36 Bhutadamara 37.
Matsyasukta 38. Mahisa-mardini 39. Matrkodaya 40. Maharitla 41 Meru
- Mahanirvana 43. Mahaklla 44. Mahalaksmi 45. Yaksini 46. Yogasvarodava;,
- Yogasara 48.Yaksa dahtara 49. Raja-rajesvari 50. Revati 51. Varnodhrti 52. Varna vilasa, 53. Vasudevarahasya 54.
Saktikagamasarvasva 55. Saktisahgama 56. Sarada 57 Sodha 58. §adamnaya
- Svarodaya 60. Sarasvati 61. Sarasa 62. Sammohana 65 Siddhi-taddhari 64. Hamsa Mahesvara
So, as I have mentioned already, the Tantrik literature is huge and it is not possible for any of us to go through everyone such Texts, more so because they are either lost or not availabe in the forms of books.
And, although Tantra is not for starters but for those who already have attained spiritual maturity to an extent, some basic books, to know what Tantra is, will be some of Arthur Avalon's books like "Shakti and ShAkta", "Principles of Tantra" etc.
The most easily available Tantric scriptures though are KulArnava and MahAnirvAna Tantram, translated into English by Arthur Avalon. Both are very important scriptures in Shaktism.
NOTE - Some errors might have crept in unintentionally during copying and pasting from the PDF. So, when in doubt better to consult the PDF directly.
Here are two more verses which say that by reading even all the Tantric scriptures available, one can not gain a knowledge of the Tantras. Learning it directly from one's Guru is the only option.
Na vedair nA Agamaih shAstrairna purAnaih suvistArai |
taporbhivA na tirtha vrata kotibhih ||
mantra oushadi purahsareih ||
AmnAye jyAyate chordhah shrimad
gurumukham vinA ||
O Deveshi, the knowledge of Urdha Amnaya (a specific portion of
Tantras) can not be obtained by extensive studies of Vedas, Agamas,
PurAnas and other scriptures, or by the performance of Homa-Yajnas, or
by performing austerities or by visiting numerous pilgrimages, or by
the use of Mantras and Oushadhi not even by any other methods --- It
is only possible to obtain the knowledge from Srimad Guru's mouth.
KulArnava Tantram 3.28,29