In general, if you go around all over Japan using JR, you have much better to use
JAPAN RAILROAD PASS which cost you over 200 US$ but you can save much money for JR fare. Every foreign visitors should learn about this in detail in advance.
As JAPAN RAILROAD PASS is only for foreign visitors, I have never used it unfortunately.
Then, if you move around KAMAKURA and ENOSHIMA area riding ODAKYU several times, ODAKYU AREA PASS might be useful to save money.
But I'm afraid you can not save money by using ODAKYU AREA PASS. Instead, I strongly recommend getting and using
SUICA : Re-chargeable prepaid card.
SUICA is much convenient than credit card in Japan. I can live on SUICA for several days without money. I can ride most of all transport system, eat/drink, use vendor machine and buy books or other staff using SUICA supported machine/shop.
Also, you can refund the unused charge in SUICA before leaving Japan. Learn it in detail at SUICA page of JR.