Okay, so how does this list sound?
1 neon blue dwarf gourmari
5 neon tetras
1 red platy
1 pineapple platy
1 Mickey mouse platy
1 red fire guppy
1 lemon cobra guppy
1 purple snowflake guppy
2 otocinclus catfish
2 peppered Cory cats
And some mystery snails and ghost shrimp. Is that overstocked? I will also be planting java moss, java fern, water sprite and water wisteria.
I agree with Delapool about Cardinals, one of my all time favorites! They are one I would add last as a group of them, about 6. I would wait about 6 weeks to make sure you have stable parameters, then after about 4 weeks of good test numbers, I would add then no sooner.
As for the Guppies and Platy, if you are wanting them for show, you might want to get all males. And see how they behave, sometimes they will get cranky with each other.
Otherwise you will constantly be having babies, and as long as you don't mind your larger fish snacking on them you might be alright.
But in all honesty that is a decent size tank, but not a big enough tank to be raising a bunch of babies along with the stock list. And you also always are having to worry about finding the babies a new home, and whether they are being/or are gonna be eaten...that can be stressful.
Also, developing a stock list is sometimes a flexible list, as you will find something great and change your mind,
.
As a new fish keeper, spend a little time searching the area lfs and the not so local fish stores for your stock.
DON'T buy a fish out of pity or think you will buy and help it.
Add stock in groups over the course of the next few months.
There are a huge number of patterns of Platy and Guppies. They will cross breed btw with their own kinds, so another reason to try males, or get one kind of Platy.
Do you have a quarantine tub/bucket/tank? After you spend all this time on getting your tank ready and picking out stock list, and stock, you don't want them to bring in some awful sickness.
I would also go with 3 or 4 Cories. And the Cories and 3-4 Otos, often you will lose one, should go in last. Or next to last. The Otos need established tank/biofilm I believe to thrive.
You might want to become a member of a local aquarium society chapter. There are some amazing Guppies, and they aren't from the local Petsmart and Petcos.
Guppy Fish Catalog here are some really beautiful examples. I have never purchased these but, just as an example of how amazing a fish can look.
These are my favorites
Green Snakeskin Guppy from Angels Plus