This is adequate to start. The air conditioner can be used as a dehumidifier also, it does remove moisture from the air.
You can potentially increase yields with CO2, but here’s the most important factor, if you don’t have enough light, this won’t do a thing. You’re just wasting time, and finances. You also have to have a sealed room for this to effective, and a monitoring device to make sure you’re over certain amounts of parts per million.
You can many different kinds of soil for cannabis. Most of use use Fox Farms Ocean Forest for soil. High in nitrogen which is great for vegging, and 3-4 weeks in (approximately) you can start your nutrient schedule. Happy frog by the same company is good too. There are lots of different kinds of soil to choose from, those are just a few examples that I know a lot of people have had great success with. I’m not sure if you’re across the pond, we may have to tag some across the pond growers.
You started out great with this option. In veg first starting out, you can pretty much keep it dimmed as much as you can. Gradually increasing throughout the veg to just under 50%. Flowering you’ll want to keep it dimmed for the stretch, then increase the intensity up to 80% or more. @dbrn32 can follow up and correct me on the settings if needed. Side lighting isn’t necessarily needed as much as top lighting is. If you want or need additional lighting, I recommend suspending it from the top for better coverage.
Send away! I’ll give you my best opinion, and there are others that I’m sure would chime in, that’s what this forum is all about. @Verdant