The ideas here may be of some use to you. http://www.gardenmyths.com/pond-pumps-filters/

I'm trying to incorporate some of that myself in an accidental pond I have, but it's smaller and my budget is pretty much nothing. We'll see how it goes.

I'm a largely clueless newbie, so take what I say with a fistful of salt, but...

If I knew for sure I wanted a pond (instead of having a pond thrust upon me, as actually happened), and I had to start with what you have, I would start by putting assorted stone in the pool: from small boulders all the way down to sand, and all easily available sizes in between. I might put in some decay-proof planting trellises up the sides as well (maybe plastic-coated steel with some earthenware pots suspended). I'd load it to an average depth of 1-2 feet, then put in just enough water to reach (not cover) the average sand/gravel surface - basically have a mostly-empty pool with a bottom of stony mud. I'd inoculate this mud with samples of pond mud and some decaying organic material, then wait 1-2 weeks. This would be to allow my janitor microbes to establish themselves before I do anything to really dirty the pond, without attracting mosquitoes.

After the needed bacteria have had some time to colonize, I would start adding marginal plants around the edges. I would give them another 2-4 weeks to establish themselves. After those are rooted and growing, I'd plant submerged plants nearer the center, raise the depth of water by about 1 foot, then add the required mosquito fish and some free-floating plants. I would try, where possible, to get my plants from wild sources, for further microbe inoculation and to bring along useful hitchhikers like snails and arthropod predators. I'd watch this carefully for another couple of weeks, see if I need to add supplemental food sources, if anything is struggling or multiplying out of control, get that kind of info and then research to see if any change is needed.

If things seem to be holding steady as is, I'd increase the pond depth to the desired level, gradually so as to give the system time to adapt (plant growth, etc). As the depth increased, I would add marginals up the sides; those too low down can either adapt, or die and be recycled into nutrients for the other plants.

I would consider adding more ornamental plants at this time, but only after the oxygenators, shaders, nutrient scrubbers, and food plants were well established. I want a low- (preferably zero-) maintenance pond, so I'd be more concerned with nutrient cycling and gas exchange than how pretty it is; but beauty can certainly come afterwards.

If I could avoid it, I would not add a pump at all; I don't want to have to do maintenance nor pay to power it. This is why I would start with the inoculated, high surface area bottom, and then give the desired plants a head start. The slime that should develop throughout the stony mud bottom is meant to serve as a recycling filter, eating garbage from the water and excreting plant-usable forms. The desired plants are there to provide oxygen, food, shelter, more habitat for janitor microbes, and use up nutrients in the water, so little is available to fuel an algae takeover.

Even if you never add any food, energy will be added to the pond over time by way of sunlight, windblown dead plant material, bugs that stop by for a drink and get stuck, anything birds drop, etc. If you're fortunate enough to start with an empty pool, and one made of something that roots won't punch a hole in, do yourself a favor and prepare it to cope with and clean up after that extra energy.