This is more a list of comments than a proper answer.
I don't know Volta Redonda but Rio is a very expensive town (for Brazil standarts)
Locals use it more than cash for day-to-day expenses meaning you also can use it to cover almost anything (make a call to be sure your it ill be valid overseas).
Also it ill take the Real x Dollar exchange rate of the day of you pay you credit card bill, meaning you ill be gaining a few dollar unless a very unexpected Real rise happens in next quarter.
Eating out means you will rely on inexpensive restaurants and fast food.
Here you ill find a lot of of Self-services and Prato Feito
In self services you (in general) pay per Kg and Prato Feito you receive a already filled dish.
In general Prato Feito is cheaper/Kg but you, like me, eat a lot less than a pound/lunch you can try a self service per Kg.
For fast food there are some franchises you maybe are familiar like Subway, Mc Donalds, Burger King.
But these are never the cheaper option. ;)
For dinner you can try some fast food & pizza delivery as usual.
Finnaly note using inexpensive options means you are unlikely to find someone can communicate in english. A good idea for start is to try to hangout with locals if you got the opportunity.
They for sure ill know the better options in town and can help explaining things and with communication.
Health & Hygiene
If you need some medicine bring it with you. First you don't know how much it's priced here second don't expect any drugstore to sel you anything without a prescription in portuguese (sounds obvious but I already witnessed a angry tourist mother trying to buy a prescribed medicine for a kid).
Drugstores in Volta Redonda
Soap sound inexpensive but sum up all that little toilet things you ill use and you see how much that can cost you. Bring at least the first week supply while you try to adapt.
Can be a concern if you cannot use a washing machine in your place you ill need to find someone to do it for you. In general paying someone to do it is a lot cheaper than using laundry shops but you ill need local help to find someone.
Eletronics, Footwear and Booze
That's where you can make some profit and use it to pay your expenses.
Due to taxation and other peculirities some stuff can be a lot more valuable here. You can try to bring a brand new iPhone, Nike, Reebok, Johnnie Walker.
Don't forget there's always unexpected expenses in a 12 weeks trip. You can become inclined to buy some souvenir for you and friends.
Locals also can try to give you the best and take to a Churrascaria or you can get used to hangout with new friends and need a third budget for the beer.
I posted some google searchs (terms in portuguese like farmácia, drogaria ~ drugstore)
If you get any question about any specific term you can try out this other SE site