The plane ticket is about 450 return from india, possibly 550. The insurance is 20. visa is 70.
You can do the Via Rhona by BIKE with 2 bags on the back wheel. thousands of europeans cycle all over france on bike and many many sleep in forests on a ground-mat with a sleeping bag and wash in the rivers, it costs 10 per day to eat, and you can cover 100km per day and have an amazing experience, but you have to arrange coutchsurfing every few days to socialize or you will be get bored. Via rhona is perhaps the cheapest and most interesting thing to do in the EU... do it with your friend from Germany!
When you arrive, you'll have to avoid hotels every time. So that means a good couchsurfing profile, because it has millions of european peeople of all creeds with free houses. and you may as well come in summer because in spring and autumn, it is often under 13' at night. So if you find some trekking friends and go trekking for a few days, it will be warm.
If you want to do it very cheap, go to one of the most increadible tourist region national parks with a little city and lots of little villages, in europe, where it is also warm enough to sleep every night, there are lots of wild places where you can hide a bag with a matress and some food and wash your clothes in the river, and see 500 year old historic villages. I am thinking particularly of Luberon national park, which is full of millionaires with porshes and huge mercedes, strange white mountains, villages made of old stones like castles from LOTR... You can go near the river and camp out in any bit of forest that you see on google maps, at night in summer it is around 17'C at the coldest at night. I went there once for 10 days with my bike it cost me $10 per day for food, 1$ for a tin of fish, 1$ for bread, 2$ for a can or something, and the rest was like fruit which is very expensive. The only thing you can't do in southern europe in the summer is light fires near the forests, ever. If you couchsurf most of the time and do a bit of bike and camping, you can get away with 12$ per day spending money plus 250$ safety money.
Hitchike everywhere, transport in europe is about 15$ per 100 kilometers, so if you go from germany to spain, that's 0 by hitchiking but you will see traffic all day for 20 days.
best go through the via rhona, research it online, buy a bike locally for 20$ on Leboncoin website and put some bags on it. 60% of french people are unable to have fluent conversations in english ( im french btw) so you have to find english speakers on couchsurf.
you can an organization in Europe which will place you with a family or a farm or a community project, or a building project, or some kind of working project where everyone helps everyone out and there are common meals at the end of the day. Those options are subject to your own persistence in networking, research and communication.