A fully insulated pool structure, sides and floor.
For your size of pool 1 skimmer would surfice, 2 is better.
A pool with round ends or angled is better hydrodynamically, producing less dead areas of water movement.
A good bubble cover, geobubble for summer and a good winter cover that keeps out the light and debris.
A filter containing Dryden Aqua AFM glass media and no (looky like products) There is only 1 AFM.
Variable speed pump and my plumbing setup (not giving out any clues in an open forum)
You could use Advance oxidation process and chlorine via either direct dosing or salt chlorinator.
A decent test kit.
Passivpool Energy "A++" rated Swimming Pools, the lowest running costs in the Universe.