Needle valve controls the flow of the co2 into our tanks, it is the fine tuning system so to speak because we need so little flow we use special needle valves.
It should be easy for you to get started co2 regs in the US are really cheap about $80 dollars which includes the needle valve and a solenoid, a solenoid allows you to switch off the co2 at night time if you dont have a solenoid you will have to run the co2 24/7.
Look up Milwaukee and JBJ co2 regulators these are very popular in the hobby in the US, one of them comes with a check valve, cant remember which one, a check valve stops the water from siphoning back into the regulator from the tank, if you buy the one without the check valve add another $20 dollar on top.
Other than that a cylinder obviously and some co2 proof hosing, you dont need a ph controller starting off this is optional and can be added later if you wish, and they cost more dollars anyway.