As the name implies, a complete skateboard contains all the parts listed above, but in an already assembled ready-to-ride skateboard. The advantage to buying a complete is it completely eliminates the research and guesswork of buying each product individually and ensures that the skateboard is assembled correctly and safely. This is the approach I used when buying a skateboard for my nephew and what I recommend for people buying a skateboard as a gift or as their very first skateboard for themselves.
Without good grip tape, skaters have a tough time staying on top of their board. The main complaints about poor grip tape tend to be that it was never very grippy or lost its grip really quickly. Once again, we recommend trusting in name brands with years of experience supporting skateboarders. Unfortunately, if you are buying a pre-made complete skateboard, you probably won't have access to the brand name of the grip.