i now have 1 icon and the remaining cores. what is the cheapest way to get the remaining 2 borders

i am BEYOND confused with these new skins and borders. ive read up on so much and i just always draw a blank.

i got the three 750s and now the disruption cache for 1500. i got the ashe icon and i want the remaining 2.

what do i buy exactly to get the remaining 2 without spending more money than i need to? i dont care about the champion icons that are just for style . thanks anyway