There are no rules for it. You can put in whatever amount you like.
(=決まりはなく、いくらでもおのおの好きな額を入れます)
1 yen is OK.
(=1円でもOKです)
Some people say it brings good luck if an amount of money has a literal meaning.
(=字にすると意味を持つ額を入れると幸運が訪れるという人もいます)
For example, “goen” which means 5 yen, can also mean “connection” in Japanese. And “nijyu goen,” 25 yen, can also mean “double connection.”
(=たとえば、5yenの意味となるgoenはconnection(ご縁)の意味とも成り得ますし、25yenはdouble connection(二重のご縁)と成り得ます)
So it’s considered lucky to offer these amounts.
(=そこで、この金額はラッキーだと考えるのです)
Oden is a hot pot type of dish.
(=おでんは、温か鍋料理の一種です)
Many different kinds of foods are simmered in broth.
(=さまざまな具材をダシ汁で煮込みます)
There are usually dumplings, fish meatballs, fried tofu, a hard gelatin-like food called konnyaku, a type of seaweed called konbu, boiled eggs, and daikon radish.
(=ダンプリングや、魚の肉団子、厚揚げ、コンニャクというゼラチンのような食べもの、海藻の仲間である昆布、ゆで卵、大根などがあります)
Karashi, which is hot Japanese mustard, goes well withoden.
(=カラシ――辛い和製マスタード――はおでんにとてもよく合います)