if you really want plants....amazon sells seeds etc...the problem is that you need to grow most of them with barely any water to start specially carpet plants
as for co2 you can buy a tank literally anywhere...
forget regulators which are expensive...get a solenoid (around 30bucks) to plug to you tank a bubble counter (5 bucks) and a pressure valve psi indicator (20 bucks)
plug the solenoid to your timer which you already own and then a pipe reducer from solenoid to aquarium piping..and make a couple splits on the piping..
one for the pressure valve indicator and another one for the control valve + bubble counter
if you can't find anybody that will refill the co2 tank after...you can open the release screw to release any pressure left in it and fill it up with dry ice (make sure to only use the max weight supported by the tank...read the label on it..---> co2 will expand when it cooled down <---)
and if you still can't find someone to sell you dry ice....grab a thermal lunch container and 10 bucks...go to a hospital and talk to any of the maintenance people
hospitals need dry ice for sample carrying..
but they throw out all the dry ice...since they can't dump it down the toilet because it'd freeze the pipes and make the floor look like a horror movie set...
so they leave it somewhere with ventilation to air dry...any of the maintenance people or janitors etc...should be able to grab you some literally for free..make sure you give them 10 bucks so next time they don't tell you to take a hike...
here was my 10gallon tank before I moved on to a 45gal
no chemicals no tabs...garden soil with rocks driftwood and some gravel...neon tetras..rainbow furcatas...endlers..snails...amano shrimp and fire shrimp
co2 on a 10h/day together with the lights and no water changes...no heaters
my water changes were literally whatever water came out when I did a monthly cleaning of the substrate
I had to top it off every 3/4 days...some people use fancy filters or risk tap water....
you got 3 ways of using tap water for tanks...one is to simply boil the water and let it cool down overnight
the 2nd would be to leave it in a bucket with an air filter in it full blast for 1 day...
and the 3rd would be to use an RO filter
either method will work just fine
I also suggest you see this video on youtube --->
the guy is a literal encyclopedia...video is about 25mins but he approaches many aspects of the hobby such as plants...nitrogen cycle etc...
And like I've said before...you went to the store and they "helped" you buy something else xD
PS: my new design for that tank will be an internal sump at 400gph!! 40turnover (a buddy of mine called me nuts xD)
I'll probably post it once its up and running...goal is 40 turnover or defeat...