Will these fish get along okay and how much do they cost?

Good job on doing your research. I would say in addition to your 2 dwarf gouramis you could get 5 or 6 of the tetras and rosboras. They are both schooling fish, so they like to be in groups of about 6. They will all get along and are compatible. I'm not really sure what to get as a center piece, most fish would probably get too big. However, you could get 4 cory catfish for the bottom of your tank. they eat small sinking shrimp pellets you can get at your local fish store. I think you are pretty well stocked. If you want live plants java moss and amazon swords are pretty easy to care for. Otherwise plastic plants can still look pretty good too. So good luck, and feel free to email me if you have any other questions. Happy fishkeeping!