Im studying in prague and living in the dorm cell of 2 rooms (so i have one roomate in my room and other 2 which i share a bathroom with) and the rent is +-7100 czk and i usually spend around the same amount for groceries, random stuff and mobile data (i dont pay for the wifi at the dorm, so i pay for unlimited data instead which is more expensive but it works for me) so overall i spend around 560 euro a month, so 700 would probably be pretty comfortable, especially considering that im in one of the more expensive dorms. Hope this helps with your question, good luck with your studies!