Hello! I have a 2.5g tank that's ready for a revamp! This will be my first great attempt at planting a tank, so be prepared there will be lots of questions

It'll be the home to a betta and probably a snail as well, maybe even a few shrimp.
Specs:
Tank: 2.5 Mini Bow
Lights: x1 15w Compact Flourencent
Substrate: Currently Gravel
Filter: Some Tiny Air Pump Filter
Heater: Um... Still need to get one...
CO2:DIY? I'm not sure- questions will come!
Ferts: I've looked for excel but I cannot find it anywhere, any other ideas?
Here's a Picture of the tank currently:
Here's where some questions come in
1. I have Miracle Grow Potting Soil, I know that I can't just stick it in the tank, but I've read that if you bake it and sift it for all of the fertalizer that it can work. Is that true? The stuff that I have says that it can 'keep plants fertalized for 6 months' is that bad?
2. If I can use the Potting Soil or some how convince my mother to get the organic kind, how much, or how deep should it be? And the sand that goes on top as well? I think that I've read about and 1/2" to 1" of each. Is that wrong?
3. I have a 15w Compact Flourecent light over the tank. I've read lots of things about plants and lights but what does that all mean? It's about 2" from the water line if even that and the water line is about 7-8" off of the substance, which will be getting deeper (the substance I mean).
4. Ferts. I have little knowledge on ferts. I know that I need NO3 and Fe and K? Is that all? What brand of these are good? I have PetLand, PetCo, PetSmart and Jack's Pets around me and all of them have a very small collection of plant stuff. So would I need to buy it online?
5. CO2. If I did any CO2 I would do DIY. But I've read that it's tricky and I really don't want too tricky. Is it even worth doing DIY CO2 on a 2.5g tank? Would I be needing a drop checker? I've seen them online and they're $15-$20, so that's a tad bit out of the price range right now. So, the bottom question for this is: Should I do CO2?
6. Plants. I have java moss, marimo moss balls, and anubias afzelii. I'm thinking maybe some kind of carpet, if possible, moss, and some kind of plant for in the back. Any suggestions? I'd love to have Dwarf Sag or Blxya Japonica, frogbits, riccia or maybe HC, but those are all probably not good in my tank.
I think that's all for now. I know, you're all probably saying to yourselves, yay, she's done asking things! Thanks for reading this and hopefully answering some questions!