Budget places can be found in almost all places. it about how much time you have and also what you want to experience decide how much it will burn into your pocket. IF looking for stay and if you interested in sharing culture you can try your luck with www.couchsurfing.com where you get to stay with people in those place free in exchange of culture and knowledge sharing and also making new friends. since i am from kerala i would say cochin-allapey -waynad-coorg or cochin- allapey- munnar- kovlam-varkala beach
There are lot of places to visit in South like if u take tamil nadu, you can visit ooty kodaikanal and on the way there are so many falls and lakes, If u want to go to Karnataka side you can travel to coorg, hampi and all near by places
Hey Puneet, Budget Places in south India for solo tripping or back packing are :- Hampi in Karnataka Varkala in Kerala Pondicherry in Tamil nadu Araku valley in Andhra Pradesh Gokarna in Karnataka Rameshwaram and Dhanuskodi in Tamil nadu Wayanad in Kerala Kanyakumari in Tamil nadu Kodaikanal in Tamil nadu Mysore and Coorg in Karnataka Ooty and Masinagudi in Tamil nadu Dre are many many places more in South India dude ... Check in Tripoto against these places and get your personal itinerary ... Happy Travelling Bro!!!
Mangalore , Udupi , Kundapura ,Murdeshwara Jog , Agumbe Chikkamagaluru 30+ beautiful places all are nearby and if u are from Bangalore. you have a very good connectivity of Bus. Stay is very cheap and you will find all type of places like beach / hill station / waterfall / spiritual places all the best