I have what should be plenty of lighting. It's a fixture meant for reef-keeping. It has 2 65W PC bulbs, one is 10,000k and the other is an Actinic. It also has an HQI Metal Halide bulb. I'm pretty sure it's 250 Watts. In addition it has these little blue LED lights for moon lighting I guess.
You have too much lighting
You will probably have an algae farm with that much lighting. For starters, I would take out the metal halide, as well as the actinic bulb. You should be able to get by with the single 10000K 65W PC bulb. You can leave the LED lights as they are.
I have a CO2 bottle and regulator and would like to find a good way to inject the CO2. I'm not sure what would be best for me and I'm not sure of the difference between a diffuser/reactor and how a bubble counter comes in to play.
A bubble counter provides an easy visual indicator of the bubble rate (how fast you are injecting CO2) into your tank. For a 30g tank, either a diffuser or a reactor would be fine for your tank.
A diffuser (in general) works by forcing CO2 through a fine, porous membrane, making many small bubbles. The small bubbles have an enormous surface area, and quickly dissolve into the water column.
A reactor, on the other hand, is usually run in-line with your (canister) filter. As the CO2 is injected into the reactor, the movement of the water forcibly dissolves the CO2 into the water.
Do you have a needle valve for your regulator? You will need one to provide fine control for your CO2.
I guess the first place I should start though is with the substrate. Right now the tank is bare bottom. I've seen some products online and I like the look of the black stuff. Are these substrates really necessary? They seem kind of expensive.
There are several black substrates out on the market today (Flourite Black, Flourite Black Sand, Eco Complete, ADA's Amazonia I and Amazonia II, etc). They are quite expensive, but can be critical to the success in a planted tank.
I do have plenty of aragonite sand left over from my reef keeping days if that'd be useful for a DIY substrate.
Any advice is appreciated.
Unfortunately, I wouldn't recommend Aragonite sand for a planted tank. You could use it, however, as long as you keep in mind their buffering abilities, etc. This would limit the choice of fish that you could keep.