Not ideal unfortunately, Betta's do not generally do well in large commnunity tanks. Dwarf gourami's are not really compatible with Betta's and a Betta would probably pick on your neons. They do not like strong water flow/current either, which i would emagine is present in a tank that size due to filtration equipment. Sorry
Great choice, zebra danio's are very hardy and very active fish and will be compatible with all of your current tankmates. A schoal of 5 or 6 would work well.