How much nutrients should I add with very hard water?

Just got my pH meter today and my tap water pH is 7.8-8.0. my ppm is 540ppm (it could be 450ppm i dont remember exactly, its 5am and i havnt slept yet so i'm a little tired).

when adding nutrients, people are saying start around 300ppm, so does that mean get my water at 840ppm? it just seems like a whole lot to me, leaving me uncertain... i picked up GH hard water micro but i just want to be cautious when it comes to actually using it and growing. it seems like at full veg/bloom i'd have ppm over 1700 or so right? oh yeah, the tap water taste horrid when not filtered if that means anything..

I want to get a reverse osmosis system but i have spent soooooo much money already for my setup, i already passed my budget. i live in a small apt by myself and just use the carbon filtered water jugs for drinking water. a RO system is really unpractical for a small-moderate grow, but if there is absolutely no other option I will get it later on. once i get a mother growing healthy, i plan on doing a SoG, so boiling all the water would probably not be a realistic option.

thanks in advance,
nobody appreciates your help

i have water that's very hard as well, around 450 ppm. good thing you picked up the hard water stuff, because i didn't however, you definitely don't want to start off at the strength they recommend on the bottle. 1/8 to 1/4 strength starting off should work.

That is a high ppm... ebay aquasafesystems - you can get a perfectly good 5 stage ro+di system for under 100 bucks. Or, check the grocery stores in your area, some have RO water for at low as 30 cents per gallon.. get some 5 gallon water cooler jugs, costs 2 buck a jug. A 20 gallon res will cost 8 bucks every two weeks, plus top off water.