i finally have some money to spend now. i am looking to buy 20lbs of premium grade base rock from reeferrocks for $31.80 + 15$ s/h. does everyone think this is a good buy?

after i purchase the rock, i will have about 150$ left over.
should i purchase a ro/di filter? or should i get the necessary equipment i will need to start up a sump(the sumppump, and overflow)?

*right now i am buying bottled distilled water from the store. for about $00.60 a gallon.