Once you have the tank filled up, make sure you have the filter running to pick up and food floating in the water column.
this would be a good time to double check the filter has been off so it’s not running dry... that will burn out the filter.
Then let the tank run over night, check it tomorrow, gravel vac again, but get your siphon started, and keep your fingers on the tube, you can start and stop the flow by pinching the tube, allowing you to target the areas that need to be cleaned of excess food, without draining too much water.
then I would pick up a bacteria supplement and dose as necessary.
after that, make sure you keep on top of water testing for the next few days, and water change as needed.