Welcome to the forum. Do not add any more fish until your aquarium has finished its cycle and the beneficial bacteria has matured enough to take on the load. As a matter you need to get rid of some of the fish you have now, more about that below.
Don't stress yourself out because we have all been right where you are now, learning. The time will be when you will be teaching others that are starting out. Essjay is correct about the gold gouramis, they get very large and can be very aggressive. My advice is to bring them back to the pet store or find someone to take them from you because they will get too large for your aquarium. Also, get rid of the siamese algae eaters because they get large and aggressive and are not really good for eating algae.
The plants in the background covered with algae are
moneywort, not sure about the little one's upfront. If you want a good root plant get a couple of
Amazon swords. There are several different species of amazon sword plants, some large some small, so do your research to learn. But they are great plants and very hardy. The moneyworts that you have are indestructible, but for some reason, they do grow algae, I have had the same algae covering my moneyworts as you have. Get a pair of scissors and cut out the tops of the moneywort and remove the parts covered with algae. Don't worry they will recover and grow again, as a matter of fact, they will take over your tank, so you will have to thin them out in the future. Solving your algae problem will take time, practice, trial, and error. You will need both root tabs and a good water fertilizer. Be careful because some well-known brands of fertilizers are snake oil, and is a waste of money. API Leaf Zone is snake oil, don't waste your money on it.
lol, snake oil is an old term used here in the States for someone selling a product that they promise will work but is actually nothing but junk. In the old west days back in the 1800's there used to be salespeople traveling around the country pulling a covered wagon with a horse from town to town. They would peddle the most wonderful of elixirs, which they promoted as a cure-all for everything, from ulcers to hemorrhoids. When the bottles they were peddling only contained alcohol and other worthless ingredients they concocted up themselves.
Right now your tank is going through a cycle, so you need to stay on top of it and do water changes, every day if needed. Don't worry the beneficial bacteria don't live in the water, they live in the filter, on the gravel, and other stuff inside your aquarium.