As they are two seperate products containing different things I would just follow the instructions for dosage. Check the contents first. You might want to start below the recommendation and work your way up. Depending on progress you might not need the full dosage, saving you some cash in the long run. Phosphate remover might be a good addition to fight off aglae.
In the long run you'll save money by investing in pressurised co2, or even more with DIY. The latter requires maybe a lot more experience though as it's difficult to control co2 levels going in unless you know what you're doing. I certainly wouldn't try DIY just yet. I use pressurised co2 from sodastream bottles. Initial outlay was half that of other pressurised kits and refills are only £10 every 3/4 months. Might be worth researching and saving up while you use liquid form in the meantime.
I don't know an aweful lot about substrate, but there are many designed specifically for plants. They're expensive though. Gravel should be fine as long as it's around 2 to 3mm, otherwise the roots will have problems finding a home. From your list only Cyperus helferi should be planted in the substrate though. Anibias is prone to rotting in substrate, prefers bog wood or rock. Same with Java Fern I believe.