Hi and welcome to the forum. Everyone has to start somewhere and now you have
The basics at the begining are all to do with your cycling, People become inpatient and start throwing fish in here, and not considering cycle lengths etc. However you seem to be following good advice and just refer to many of the cycle threads within the forum.
What I would say is it is actually harder to keep a smaller tank than a larger one as you "get away" with more harmfull affects in a large volume of water. However most newcomers beleive a small tank is more manageable. Small tanks can look GREAT however you will need to watch the water parameters extremely carefully.
In regards to plants, I personally would advise them to go in Straight away, they take in and use up harmfull aggents in the water which is what you are trying to iliminate as much as possible if cycling with fish. The waste from the fish will help build the beneficial bacteria within the filter (Hardly any in the water)
If you choose to fishless cycle you may wish to add the plants, figure out which wayu you would like to cycle, check the guides on here, as there are experts who have made "idiot proof" guides how to do so.
Plants will help you greatly in the long run, as it will act as a natural filter, provide food to certain fish, provide shelter for other fish, and provide a more natural environment (both to look at and the fish to live in)
Platys are a great fish as there hardy enough for the beginner aquarist, and come in a range of colours (the mickey mouse platys my favourite

)
My essential advice to you is

(1) Test the water often
(2) Be Vigilant in your water changes
(3) Learn from your mistakes, as you will make them in! We all have.
(4) Enjoy the learning Curve of fish keeping
Welcome to the Forum and dont hesitate to ask Q's in the forum
