Sand - Beautiful. I have it in both of my tanks. It's fairly easy to clean. As long as you get a good brand. CaribSea SuperNaturals is what I use for my 20G... It's fine grained, and it doesn't cloud my water at all... It also never altered my parameters. :D Just be sure to clean it very well at first, rinse, rinse, rinse! Fish poop and other wastes also don't go under the sand, it stays on top. Very hard to see, if you choose a nice complimentary color.
For cleaning, just hover the siphon over the waste thingy and the siphon will suck it right up. :) Just don't get too close. Also, if you will get a filter, turn the filter off until the water change is done.
Gravel - I used it in the past. Natural looking, as long as you keep the algae under control. Food and waste fall in between the slits. It'll take longer for the water change to complete. I recommend Top Fin. (:
After you add the conditioner, the water is ready. Aging the water with the conditioner in is just a waste of time.