Your cheapest route may not necessarily be the best route to overclock your GPU of choice you will need a full coverage GPU water block, because the full coverage block allows excellent memory cooling, and a cooling kit like the XSPC Rasa RX240, however the Rasa kit does come with a CPU water block, but it is probably the cheapest route to procure the kit.
After looking at Amazon, that route is seriously going to limit what you can acquire, but these are my recommendations for whatever you decide to do.
And this is the minimum water cooling kit I suggest you go with for your intentions.
For the results in bitcoin mining, the amount of energy you are using to get the dividends is still a negative for the end-user.
Unless for some reason you don't pay your electric bill, this really isn't a viable way to make money, when you are spending money to power the rig to make money.
However, getting past that point and wanted to address this:
This will be my first setup and I have read a lot about the precautions, that I why I have decided liquid over water, liquid can be non-conductive.
Most people only use distilled water- which initially is non-conductive. However, any 'coolant' you use that claims to be non-conductive will ultimately become conductive in a short amount of time...even within minutes and hours.
So I have $250 to spend on Liquid Cooling just the GPUs.
This likely isn't going to be enough to start your watercooling venture. Finding used parts might help, but finding GPU blocks for your needs might not be so easy unless you go universal, which also means you have VRM, MOSFET and vRAM to cool which will need RAMsinks. The kits you mention are almost always a CPU beginner's loop and you'd still need to purchase the GPU block for the video card being used.
You'd still need a pump...and a reservoir doesn't do anything for your cooling ability; it simply holds water. Once the loop working equilibrium, the water volume doesn't matter.
Going by that reservoir you have listed, you'd need a DDC.
For now let's just worry about $200 WITHOUT the GPU Blocks.
I'm not sure I follow your reasoning- you're still looking at another $120 (universal blocks) or $230 (full cover blocks) outside of the reservoir, pump, radiator, fittings and tubing needed to complete this project. Splitting it up still doesn't detract from the need for all those components before it's a functional loop.
Not linking the Arctic cool thing yet rubix? http://www.tomshardware.co.uk/cooler-gpu,news-38479.htm...
Just joking Op, stick with the original plan here
360 rad, res/pump and universal blocks with heatsinks for Vram/mosfets
The RX240 kit rubix listed is good, I run a modified one but for two cards I would make it the 360 version (just a bigger radiator)