Timing Belt Parts Needed for Full Replacement and Water Pump

I want to pay to get my timing belt and water pump replaced. However, I want to purchase all of my own auto parts in order to get this job done. What are all the parts needed in order to do this job on my car? 

I am looking at a new timing belt replacement kit online that includes the following: "timing belt kit with seals. Includes: Timing belt, balance shaft belt, camshaft belt tensioner, camshaft belt idler, balance shaft tensioner (hydraulic actuator not Included), two camshaft seals, crankshaft seal, pre-assembly seal lubricant; water pump driven by timing belt, interference engine". 

Is it necessary to get all of these in order to do a thorough job? Or would I need to purchase a timing belt idler pulley and a timing belt tensioner as well? This kit plus these two belts is still more affordable than this second kit.

There is an alternative timing belt kit that I found online, which includes: "applications include interference fit engines; kit contains: Timing belt, tensioner pulley, idler pulley (if applicable), hydraulic damper (if applicable), water pump and gasket, balance shaft seal (if applicable), camshaft seal."

Would it be better to purchase this second kit, which is more expensive than the first kit plus the timing belt idler pulley and tensioner? Is the hydraulic damper and water pump gasket necessary? My car is past its half-life but still on the original timing belt and I do not believe any of the other parts have been replaced, like the balance shaft belt and tensioner and the damshaft belt tensioner and idler. 

I am looking to save money any way possible, but I want the job to be done well.

Thank you, I appreciate any answers! Sorry for all the questions, any feedback would be very helpful.