How much line should I buy?

I've got probably 6-8 Garcia 6500 c3's I need to put line on. Im gonna be using 65lb power pro and trying to figure out how much one will hold and what length spool to buy. I know they sell in 150 and 300 yard lengths pretty common and I can order bigger spools online so if for example it held 100 yards it would be more economical to buy the 300 yard rolls..

Buy the 1500yd bulk spool and be done with it. I can fill my 8 7000s with 100lb power pro and still have some leftover. Its usually about $130