Here's a relatively cheap hybrid thorium plutonium 4 chamber 220EU/t Eff 4 Mark I reactor (3 double thorium cells and 4 plutonium cells twice). I wanted to reduce the non-renewable copper while getting more EU/t. Checked with GregTech computer cube to be stable.
Here's a quick change to SSD's really cheap breeder to double output and make it be automatic (via BC/RP) (per cycle).
And finally a simple way to make your reactor/breeder automatic* (for 1 cycle). The manager to the left has nothing set and the chest it controls has only enough materials (plutonium cells or depleted isotope cell) to complete one cycle. The emerald pipe to the right extracts (can be re-enriched cells or near-depleted ones) with an autoarchic gate set to "items in inventory = pulser".