>>605089>>605505Cost-effective or good? These are two opposing requirements.
If you're overclocking, a pair of single-rank sticks as fast as you can afford.
If you're not, a pair of double-rank sticks that support the highest DDR4 standard your board does.
If you want cheap instead of good, then either 2x8 or 4x4 or 2x4 or 4x2GB (whatever's cheapest) at whatever speed is cheapest. For a given speed 2x8 will probably be slower because probably no rank interleaving, but RAM performance isn't really that important anyway.
Don't buy RAM with a tacticool heatsink on it: RAM doesn't need a heatsink (as only 1/4,000,000,000th of each die is actually doing anything at any given moment), and the companies that make RAM sticks don't actually make RAM chips, they just solder on the exact same chips as everyone else.
