This will be VERY brief, not at all comprehensive, and maybe only marginally useful, for fear of listing incorrect information, and to avoid basically typing in whole the very articles I just read.
A geography lesson of the Indian sub-continent is beyond the scope of this article, but here are some helpful hints on the languages and areas mentioned here. Modern Rajasthan is located in the central western part of the country, and encompases Udaipur, Jaipur, Jodhpur, Bikaner, and Kota, among others; in short, the Rajputs. Languages spoken there include of course Rajasthani, but also Marwari, Mewati, Jaipuri, Harauti, Mewari, etc -- all Indo-Aryan languages. Modern Karnataka, located in the south of India, encompases a good deal of what in period was Bijapur, and roughly half of the Vijayanagara kingdom. Kannada, a Dravidian language, is the primary language spoken there, along with Tamil, Malayalam, Telugu, (also all Dravidian languages), etc. Marathi is an Indo-Aryan language spoken in what is now Maharashtra, located just to the north of Karnataka. Bengali is another Indo-Aryan language spoken in what is the modern state of West Bengal and the nation of Bangladesh, both in northeastern India. In period this area was simply known as Bengal.
The majority of Indo-Aryan languages all derive from Sanskrit. Dravidian languages, however, are an entirely separate language family. This did not keep Sanskrit from heavily influencing the vocabulary of Dravidian languages, of course, most obviously Kannada and Telegu (the northern-most of the Dravidian languages; Tamil, further south, is less Sanskrit-ized).
This article is intended more as a guide to recognizing placenames, rather than on how to create new ones from scratch. If you absolutely must, however, it would be good to know the general patterns listed below. Placenames were sometimes used in an individual's name, greatly dependent upon specific language/culturel; far more common were kinship names of some type.
-pur is a Sanskrit suffix meaning "city". There are quite a number of suffixes, for several language groups, many of which are Sanskrit or Sanskrit-derived ("modified" slightly to fit in the local language group; for instance, you find the same suffix as puram in some south Indian areas).
Placenames frequently (but not always) have a suffix, which is always generic (town, village, hill, etc).
Common suffixes in what is now modern Rajasthan are: [1]
pur, puri, pura, mer, ner, gadh, gadhi, dera, waro, khedo
Suffixes in Karnataka placenames are: [2]
uru, suru, halli, palli, pura, ge, gi, game, grama, gao, gundi, gunda, kere, gere, sandra, samudra, ambushi, bhavi, betta, kal, gudda, kunte, guli, eru, wole, hole, bana, baylu, karu, gadde, koppa, kuppa, gondi, kuppe, sara, gola, vara, wada, gudde, kundra, kunda, vanti, katte, guli, kuli, mavu, vatta, gatta, kadu, hitlu, mangala, bidu, bagilu, tota, mane, koti, kote, varam, bele, hatti, palya, etc.
Suffixes denoting geographical peculiarities common in placenames in Karnataka include: [2]
-kani (-gani) "mine" -kadu "forest" -kunda (-gunda) "elevated place" -kutta "hill" -kuli "pit" -kodu (-godu) "border" -gudda "hill" -jali "name of the tree" -bidru "bamboo" -betta "hill" -maggi (-magge, -mogge, -makki) "elevated place" -mallige "jasmine" -mavu "mango" -vatta "road" -sara "row of trees" -gatta "ghats" [4]
I don't know if the forms in parenthese are dialectal variants or different grammatical forms.
The suffix -palli is from Telegu, not Sanskrit. Likewise, -gao seems to be a Marathi language suffix. [2]
Some Bengali suffixes are gram ("village"), khari ("bay"), nagar, para, and tala. [3]
Towns and cities are named for:
Jaipur (Jai) [1]
Jodhpur (Jodha) [1]
Kumaranahalli (Kumara) [2]
Nayakanahatti (Nayaka) [2]
Byrapura (Byra) [2]
Bhilwara (region/enclosure of Bhils) [1]
Merwara (Mers) [1]
Doondhar (Doondh- hilly)[1]
Soodsar, Napasar (-sar "natural depression") [1]
Doongarpur (doongar - mountain) [1]
Kalluru (kal- stone) [2]
Kaduru (kad - forest) [2]
Betturu (bett - hill) [2]
Mulgunda (mull - thorn) [2]
Amli (imli tree) [1]
Pipalaya (peepal tree) [1]
Kherloo, Kherli, Kherdhar, Khejri (kher or khejra tree) [1]
Nawiluru (navilu - peacock) [2]
Handiyuru (handi - pig) [2]
Kolihalli (koli - hen) [2]
Palasandra [2]
Gangasandra [2]
Haldighati ("yellow valley", from yellow soil) [1]
Kali Pahari ("black hill") [1]
Ratighati ("red valley") [1]
Arbud (hill of Buddha) [1]
Ramanathapura (Ramanath) [2]
Ramakrishna Gram [3]
Brahmpuri, Bamanvas (where Brahmins live) [1]
Charanvas (Charans) [1]
Khatipura (carpenters) [1]
References & Notes
[1] Book of Indian Names, edited by Raja Ram Mehrotra, "Place names in Rajasthan" by I.K. Sharma.
[2] ibid, "Toponomy of Karnataka" by H.M. Maheshwariah.
[3] ibid, "Place Names of Andamans" by N. Francis Xavier.
[4] Best I can tell, it means literally a "landing", like along a waterway, but was expanded to mean center of trade.