If it were me (and it is not), I would start with getting the depth and contours the way I wanted and sealing the soil. I would want to have the depths right to discourage excessive plant and algae growth, and make sure it holds a reasonably stable water level. Next, I would add a way too access the pond without mudding it up. For me, that would be a dock. I would then establish desirable marginal plants to take up excess nutrients and add beauty. I would do this sequentially since the depths and water-holding ability are critical. I am no expert, but I do have a couple ponds and have learned a lot on this forum.