Hi fluffypants and welcome.
That will be too many fish for your small tank. Save money and stop adding the fertiliser, Stress Zyme and water conditioner, they are not needed.
You will not have cooked the plants at 28C and by now you will realise that 25 on the heaterstat doesn't necessarily mean 25C :roll: .
Neons are not good to start a tank with as their quality seems to leave a lot to be desired these days and they will most likely die in a newly set up tank. The zebra danios would be excellent to start with as they are hardy. 6 of these would cycle your tank nicely. If you start with them, do not add any more fish for at least 1 month to give the bacteria time to build up in the undergravel filter. This is what we mean by "cycle". As the fish produce waste, this is converted by good bacteria into harmless stuff and builds up slowly over time. If you add too many fish at once they will die from ammonia poisoning as the new bacteria can't multiply fast enough to keep up with the wastes produced.
Guppies and platies are livebearers so will produce fry every 4 - 6 weeks - hundreds of them! If you do not want this, as you will have to have somewhere to put them, get all males. Otherwise, you want a ratio of one male to every 3 - 4 females.
I would not add a Siamese Fighter (although many will disagree with me) I feel they are better suited to a species only tank of their own.
Dwarf gouramis are sensitive to water conditions so don't add them either until the tank has matured a few months and stabilised.
How about attending the next Totally Tanked meeting? Check out
http://www.fnzas.org.nz/fishroom/februa ... 18496.html
They will be able to give you a lot of help (and maybe fish and plants too ) and help you work out what is best for your tank.