What really needs to be addressed, seriously, big problem, is not the plants or the sand, it's the fish.
2 tiger barbs
2 zebra danios
2 serpae
2 black skirt tetra's
2 red eye
2 glow tetras
3 white clouds
1 cory cat
1 pleco
4 neon tertas
The only fish you have in here that should not be kept in group of at least 6 is the pleco, which is going to quickly outgrow your tank.
Not only that, but the tiger barbs are going to be a gigantic problem. They might not be now, but trust me. They will be.
I know about the attachment thing, yes, you like your fish, that's good
but if you like them, you should be able to make them comfortable, and they are not going to be comfortable in mere pairs. They'll be more skittish, and more prone to disease, especially not if, but once the tiger barbs become mature and begin to harass their tank mates.
Here's my advice, take it or leave it.
Step 1: Take the tiger barbs back to the store. They might not be pesky right now, but looking at the picture you provided, they're still young. They'll only get worse. Tiger barbs are monsters.
Step 2: Take the Cory Cat back to the store. You said you don't have a lot of money, and cories tend to be rather expensive.
Step 3: Pick out your favorite 2 species of the massive amount of tetras you get. Keep your two favorites. Take the rest back, and get more of your two favorite species. Up their numbers to at least 6.
Also, once your pleco passes, or better yet, if you can find somebody with a tank big enough to hold one, pick out a smaller pleco to take its place. Like a bristlenose pleco. Common plecos get up to 2 feet long, they're really not too suitable for average aquaria.
When you have money and sand substrate, buy 6 cory cats for ground crew. you can also pick out a centerpiece fish, (a fish that doesn't school, like a gourami or peaceful cichlid or betta depending on your stock) make sure to research the fish you pick out. Make sure your tank is large enough for them, the water perimeters in your tank are safe for their preference, and make sure they are not aggressive.
If you ask nicely, you might be able to get some in store credit for the fish you bring back to up the numbers on the two favorite tetras.
I can't go without this being said.