First of all you must decide what you can provide for a planted tank. Is your tank low light, medium light, or high light. You must also decide what plants you wish to keep. You must research the needs of the plants, soft, acid water, neutral water, ect. Oh, and by the way, you will need to see if your fish will eat or destroy plants.
Now, having done your homework, you can decide on whether or not you want to spend the money for upgrades. Things like lighting, CO2 injection, timers can be not only useful, but necessary. The first two upgrades I would make, if warranted, would be substrate and lighting. Substrate for sure and lighting if needed. CO2 injection can be an expesive deal. Just the hardware, controllers and valves, ran me $150 and that did not include the tank or CO2!! Timers are nice for the lighting, but they can also be used to control the CO2 system. My timers ran either $49 or $79 each and those were a semi-basic timer/power strip. The newer systems I have, the timers, again, cost about $149, but they provide power to the entire system, including moonlights.