Is the tank fully cycled?
If you can wait at least a couple more weeks, then add 4 more white skirts. That'll make the tank more interesting for you while you wait for it to mature enough to add otos (at least 3 more months from now). To be honest though, if the only reason you want them is to control algae, you may as well get an algae scraper. Otos aren't active fish that'll realy entertain you or impress friends. I've already mentioned how fragile they can be. They need excellent water quality at all times. If you like them for what they are, by all means get a few (2-3 idealy) but, otherwise, it's not worth the trouble. The dwarf gouramies would be fine to put in a couple of weeks after the skirts. Just make sure the tank's got plenty of hiding places for them by then. By floating plants I mean any species of plant that floats... duckweed, lilies, even elodea, are all examples. I should add that with 2 dwarf gouramies, 3 otos and 6 white skirts, your tank's then fully stocked so you shouldn't add any other fish (at least until the tank has been up and running for a while and all the fish are fully grown and still going strong.