Edmonton Freshie walking the plank, Any advice to ease the wallet/headaches :)

[Hustler]

Hey all,
Im mel from edmonton.
I am a long time freshwater keeper zero hours saltwater newbie
My 300 has a giant sump with room for a skimmer,
I would love to do a reef setup with a community of fish and critters and right now I am trying to price out a rough cost to get going...
from what Ive gathered so far ill need,
-Salt
-Skimmer
-Big mother lights
-Live rock/live sand
-water/light measuring tools
Here is what Im working with right now,
300 gallon 96x24x30 with a 6x18x24 sump and a Giant pump (from pices store rack system) Tons of mag powerheads and fresh water drip automatic system with chlorimine carbon filters run into the tank and drains to the sewer.
Where I am at right now.......
its still up and running fresh, so Ill dump it and scrub everything dismantle the sump and figure out how to rebuild it for salt IE no bio balls or sponge or adding new baffles protiene skimmer, reactor ect ect and go from there as a brand new build.
I will probably do half live rock and half base, do i need to go with live sand?
Can i fill it with filtered tap water and comercial salt mix or do i have to go with an RO unit? would it be safe for the live rock so i can start the bio cycle?
Im in no hurry for fish and corals but I would like to set it up right the first time and have a good base to pick and choose where it will eventually end up
any advice is greatly appreciated..... I hope to get into meetings and whatnot here soon once i know what im doing LOL