Random musing on QI theory.
You want 1 pillar per 5CC of casting cost.
There are 12 elements. Quantum Pillars produce 3 random quanta. On average, then, 25% of elements get a quanta per turn -- or, statistically, each element gets .25 of a quanta per turn. Therefore, with 4 Quantum Pillars, you get the same net effect as though you had 1 pillar of each kind -- statistically.
So, in order to find the right number of pillars in a half-rainbow deck, you need to find the one sub-element that has the highest total CC, divide that by 5, multiply that by 4, and then add that many Quantum Pillars. Then, with your main element, subtract 1/4 of your Quantum Pillars from the total number of on-element Pillars you put in.
So, for example, if you have a half-Light deck with 46 total CC in Light, and the other half is rainbow with the highest CC being a Toadfish (5), you need
5/5=1x4=4 Quantum Pillars, and
46/5=9-(4/4=1)=8(-1 for a Light Mark)=7 Light Pillars. Total of 13 pillars, 4 Quantum and 7 Light.
No idea how to take Novas into account; I usually just swap them out 1-for-1 with QPs.