There are many things to take into consideration. Some "harder to grow" plants "need" CO2 injection, and some don't. Maybe a list of the plants you intend to place in the tank would help.
As a general rule, darker green and faster growing plants don't "need" CO2. Red and brighter green plants benefit from CO2 injection.
Also, you also need to consider the gas exchange of the water. A tank with a larger surface area is less likely to need CO2 supplementation. A taller or "show" tank is more likely to need supplementation, because there is less surface area to allow oxygen/CO2 exchange.
Basically, I would get good lighting, a good substrate, and give it a while before trying CO2 injection. CO2 is used by plants during the day. But, at night, the plants use oxygen (in respiration) to produce the food and other elements necessary to get them through the night. So, excess CO2 in the water at night, soften the water. Then, during the day, the CO2 is used by the plants, returning the water to its true pH. This is the cause of the pH fluxulation. This, with a moderate-low level of injection/supplementation, will only make a small difference in pH tolerable by most fish. If keeping sensative fish or needing large amounts of CO2 injection, I would suggest a "liquid CO2" addative. This can be added daily in the AM, thus the CO2 will be used up by lights out. In a larger tank, say 50+ gallons, you can use electric reactors, but aren't reasonable for small aquariums.
Plus you can fit a lot more plant in a 10 gallon. gl wiht your decision though
