Kamala Yantra along with its Mool Mantra is considered very effective medium to fulfil Kamala Sadhana.
ॐ ह्रीं अष्ट महालक्ष्म्यै नमः॥
Om Hreem Ashta Mahalakshmyai Namah॥
Ashtottara Shatanamavali of Kamala
list of Kamala Mantras
information on Goddess Kamala
10 forms of Shakti