Firstly, I strongly recommend that you fish-less cycle your tank before adding any fish. The sort which involves addition of ammonia and a liquid test kit, not the sort which involves sitting the water in a tank for a week.
Secondly, you haven't picked the best fish ever to start with, but I will explain about it in a bit.. you should be looking at this sort of stocking:
* 10 neon tetras
* 6 male guppies
* 6 dwarf/pygmy Corys (who do best on (play)sand, not gravel)
..which leaves room for a few more additions.
So, now to why they might not be the best choices..
* Neon tetras can sometimes be very fragile, so a lot of people on this forum will recommend that they are only added to a 6+ month old set up. Personally, I have never had a problem adding them to a new, planted set up with the right water parameters (pH 7.0 or lower, hardness medium or softer). They are known to be not the hardiest fish ever so if you get them, do be prepared for problems.
* Guppies are again quite a fragile fish.. very often, because they are inbred. It is normally well worth while finding a good breeder if you want to keep them, rather than buying them from an average shop. Note that some shops will take fish in from normal people, like you and I, and those fish tend to be the healthiest. They are very prone to fin rot.
On the other hand..
* Dwarf or pygmy Corys are quite hardy, and are pretty much the only bottom fish you can have in a tank that size..
* Plants will help the fish feel more secure, so you are more likely to have luck with your fish.
* If you take your time to find healthy fish and properly cycle your fish tank, your chances of success will also be greatly improved.
* It is good practice to have medication at hand, regardless of which fish you keep anyway.
* Schooling fish, such as neons and Corys, really do benefit from schools, so you're already on the right track here. Even though we recommend 6 as a minimum, in my experience, most of these fish do best in groups of 15-20+ and with few species (as I suggested above), you could raise the numbers for both slightly (for example, to 15 neons and 8-10 Corys) with time.