The short answer is that you use ALL of them. Each command is used to solve a small problem. You combine commands to solve bigger problems. You then combine routines, loops, and functions to create a program.
You've got to read the manual or help files from beginning to end so you know what commands are available and how they can be used to solve problems.
After that, sit down and DESIGN your game. Break out the pencil and paper and write notes about game features, draw sketches of the user interface, and create charts that show events and features are related.
RPGs can be brutally complicated to create. I suggest starting with easier programs so that you can gain experience in writing commands and logic structures, displaying graphics, organizing data, etc.
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TAZ