just be aware that the price of a helmet and how well it protects your head have nothing to do with each other.
a $100 DOT helmet will offer the same protection as a $500 DOT helmet. a $100 snell helmet will offer the same protection as a $500 snell helmet. (and snell rated helmets do not necessarily offer better protection than a DOT only rated helmet...some argue they offer less protection because they are too hard and transmit too much force to your head instead of absorbing it by crumpling in non-race speed crashes).
more expensive helmets are often ligther, flow air better, have removeable liners for cleaning, are more comfortable, etc., but they do not protect any better. if you are on a tight budget, you can buy a cheap helmet (as long as it meets whatever safety certification you believe in) and feel confident your head is protected.