your stocking isn't good really but it's what I would expect from a beginner so don't get hung up about it. We've all made mistakes to begin with.
Basicly you've added lots of different tetra's when it would have been better to add a large shoal of just one type. When it comes to shoaling fish such as tetra's they do better in groups of 10+ ... not only do they behave naturally but you get to see a nicer effect - watching them shoal naturally is lovely to watch and the more you have the better the shoal and visual effect.
There's a chance that the black widow's will pick on the guppies and start fin nipping. This type of tetra is well known for fin nipping and with the guppies flowing fins it may encourage this behaviour.
The tetra's and plecs are soft water fish but the guppies, swordtails and mollies need hard water - the mollies would prefer hard and brackish (this means aquarium salt added) too so not a good mix there as the plecs though can not cope with brackish water
As I said, don't worry about it now. In time you'll get your stocking right. It's all a big learning curve to begin with.
With your lighting ... it's best to give at least 8 hours of lighting for the plants to thrive and don't be scared of plant ferts/Co2 ... there are instructions on the bottles and all you need do is look at the amount needed for water volume. As mentioned before, I use Easylife Profito plant fert and it tells me to add 10ml per 100 litres of water, per week. My tank is 240 litres but I have large lumps of wood and some rocks so to make it easy I've allowed for this and removed the 40 litres from the calculations so I'm adding 20ml of fert to my water volume. It's better to be a little bit under than over as the plants will also use fish poo and nitrates as food aswell.
With the liquid Co2 (easylife's easycarbo) It tells me to add 1ml per 50 litres with a maximum of 2ml per 50 litres for aquariums with lots of plants so I add about 4ml per day.
You can get small syringes or pipette's easily online (amazon, ebay etc) really cheaply which will make your life easy when adding ferts/Co2.
When buying plants - try to avoid those with the ceramic base as this tends to stop them developing roots as they rot at the base. If you have no other choice than to buy those cut the ceramic thing off ... plants like cabomba, elodea (which are the main two they fasten to those ceramic ring things) will re-root themselves in time.
If you buy a plant in the mini plant pot remove the plant pot and as much of the rock wool as you can that's in there too before adding the plants to your substrate.
There are two types of plant that can't be planted in the substrate, these are Anubias and Java fern. These need to be tied to decor - you'll probably see these already tied to wood in p@h.
If you are unsure what a plant is, ask them. If they don't know you can look them up online. Try looking on Tropica's website as they normally give clear pictures and descriptions of all the plant species.
Hope that helps and I've not overwhelmed you with info