Who were the parents of Bhumi Devi,the Goddess of Earth? (If any) Can someone say in which purana her origin is mentioned?
In one Samvarta Smriti (Samhita) verse (74th from Chapter 1), Earth is mentioned as an offspring of Lord Vishnu.
The first offspring of the Fire is gold ; Vishnu's offspring is the earth ; and kine are the daughters of the Sun. By him, who makes gifts of gold, earth and kine, three regions are given away. (74)
But this is surprising considering the fact that Lord Vishnu, in his Varaha avatara, has Bhu Devi as his consort.
I'm unable to find the entire Samavrata Smriti (in English) online currently although I have downloaded it years back. But I have found it in Sanskrit only here.
The verse I have given above can be located in Sanskrit on page 6 (out of 18) of the PDF.
Agnyer apatyam prathamam suvarnam bhur-vaishnavi suryasutascha gavah |
Lokas-trayastena bhavanti datta yah gashcha mahishcha daddat ||
The translation is already given above. In this verse Earth is mentioned as Bhu (in Bhur-Vaishnavi) and as Mahi as well (in mahishcha). The first half of the verse is talking about apatya (or offspring) of Agni, Vishnu and Surya respectively.
Lord shiva n mata parvati are the parents of bhoodevi. Not only her but they are also the parents of the panch mahabhootam which includes water, air, fire, sky and earth. So lord shiva is also called panchbhooteshwara which the one from whom all the five elements were created and who have control over them and he is also called bhoodeva which means the lord of the earth. There are also temples of lord panchmahabhooteshwaram or panchbhooteshwar or bhooteshwar am in the south. Which also is mentioned in shri ghagwat gita. Om...🙏🙏🙏.
According to Rigveda...
The verse RV 6.49.10 calls Rudra as " The Father of the Universe" (bhuvanasya pitaraṃ)
bhuvanasya pitaraṃ ghīrbhirābhī rudraṃ divā vardhayā rudramaktau
bṛhantaṃ ṛṣvamajaraṃ suṣumnaṃ ṛdhagh ghuvema kavineṣitāsaḥ (RV 6 :49:10 ) 
Rudra by day, Rudra at night we honour with these our songs, the Universe's Father. Him great and lofty, blissful, undecaying let us call specially as the Sage impels us ( RV 6.49.10)
The verse RV 2.33.9 calls Rudra as "The Lord or Sovereign of the Universe" (īśānādasya bhuvanasya)
sthirebhiraṅghaiḥ pururūpa ughro babhruḥ śukrebhiḥ pipiśehiraṇyaiḥ
īśānādasya bhuvanasya bhūrerna vā u yoṣad rudrādasuryam ( Rig veda 2:33:9 )
With firm limbs, multiform, the strong, the tawny adorns himself with bright gold decorations: The strength of Godhead never departs from Rudra, him who is Sovereign of this world, the mighty.
I hope this explains that lord shiva is the father of universe so maa bhoodevi (planet earth) n all other planets were created during the creation of universe itself by the tandav n laasya of lord shiva n maa gauri which was again stated in Shiva Maha Purana. That's why bring the purusha and prakriti they are also called jagat pita and jagat mata.
“somaḥ pavate janitā matīnāṃ janitā divo janitā pṛthivyāḥ | janitāghnerjanitā sūryasya janitendrasya janitota viṣṇoḥ |” (Rig Veda IX.96.5)
“Father of sacred chants, Soma( Lord Siva or Rudra) flows onwards, the Father of the Earth, Father of the Celestial region: Father of Agni, the creator of Surya, the Father who gave birth to Indra and Vishnu”
See this: https://m.patrika.com/gwalior-news/1000-year-old-shiva-temple-are-mentioned-in-geeta-1361061/ https://isha.sadhguru.org/mahashivratri/shiva/shivas-names-108-shiva-names-with-meanings/ https://www.templepurohit.com/hindu-temples/pancha-bhoota-lingams/ https://en.m.wikipedia.org/wiki/Pancha_Bhoota_Stalam https://www.goodreads.com/work/quotes/140104-siva-the-siva-purana-retold https://www.templepurohit.com/kashmiri-shaivism/amp/
According to various passages in the Rig Veda, the earth (pṛthivi) was not born. Rather, it was manufactured by 'the poet' (kavi), seemingly referring to Tvastr, who is a sort of maker-god.
This is most clearly expressed in RV 1.160.4 - "This is the most skilful of skilful gods who produced the omnibenevolent Sky and Earth, Who carefully measured out the two atmospheres [and] adorned them with undecaying pillars."
RV 4.56.3 and RV 3.54.6 also refer to this same event. All the devas were then born from the Sky and Earth. I have written a bit more about it here.