Bettas should not really be kept with other fish, and definitely not with gouramis.
A group of female bettas is called a sorority. They should be the only fish in the tank and in a group of at least 4. They may be females but they are still aggressive fish. One female is OK (provided there are no gouramis); with two, one will pick on the other; with three, two will gang up on one. With four or more the aggression gets spread out and no one fish gets picked on all the time.
Dwarf gouramis are often infected by dwarf gourami disease, which is incurable and fatal. A lot of shops will only sell dwarfs as a male/female pair and some do not stock females because they are "so plain and boring no-one will buy them" (females are plain silvery grey with perhaps a hint of colour)
Personally, I would go with a different species of gourami.
Emperor tetras are active fish and will stress out placid gouramis.
I would go for the two tetra species, cories and rams. Since you want two female rams there shouldn't be a problem with the cories getting attacked by spawning rams. Then once the tank has been running 6 months, get some otos. You need to wait until the tank has matured and grown algae before getting these fish.
But as Cod says, make sure you have soft water. If you don't already know your tap water hardness, it should be somewhere on your water company's website.