I actually find sand is much easier to clean than gravel, as poo/detritus/uneaten food settles between the grooves in gravel, while it just sits on top of sand until you can vacuum it up. It takes a bit of time to get used to cleaning it, but it's a breeze compared to having to vacuum every inch of gravel substrate to get all the crap out, in my opinion at least.
I also find plants do better in sand (not to say that people don't have gorgeous planted tanks with gravel substrate), just that in my personal experience I've had better luck with sand.
Aquarium safe twigs are fallen dry dead twigs that I collect from a hard wood tree in my yard and soak, then place in the tank. I say aquarium safe because I don't want anyone to get the idea to go break sticks off a random tree and plop them in a tank, that's just asking for trouble! :)
You can google pictures of "natural planted tank" or even look at underwater images of rivers, lakes, and streams. This youtube video is one of my favorites, showing the natural habitat of some common aquarium species.
You can arrange it any way you'd like, but for best viewing I always place taller plants (amazon swords, stem plants) in the back, and shorter plants (small species of crypts, dwarf sag, etc) in the front.
Most people set up their hardscape (sticks, driftwood, stones) first, and then plant around it, so the hardscape looks like a part of the scene. It takes some fiddling for people to find what they like best, and you may decide a few months later you don't like it anymore and decide to re-arrange, which is totally okay! I've re-scaped my tanks hundreds of times.
Aqadvisor is...tricky. While it's a good tool to use when trying to stock a tank, it's just that, a tool. It can't be relied on to do all of the work, a lot of that comes down to the responsibility of the owner. The neons and the lemon tetras are both mid-schooling fish, so they're going to take up all the space in the middle section of your tank. They're not a bad choice for a ten gallon, but I'd say with just the 12 of them you're at your limit with stocking, not to mention the 3 otos.
The reason dwarf gourami aren't advised in pairs or groups in small tanks is because they aren't really peaceful at all, they're actually rather aggressive and territorial and if put in a small space will almost always endlessly fight. Gourami are a tricky species, the same with Rams. They really, really need a lot of space (looking at 29 gallons bare minimum) to be able to be housed as anything more than singly.
I wouldn't recommend either of those species for your ten gallon, though, because you're really at your limit.
Most fish feel safe when having places to hide, ie behind large plant leaves, stones, pieces of driftwood. And since most aquarium fish are forest dwelling fish, they take comfort under dim lighting and a covering of floating plants.