sorry im not a great or wise user and frankly, i have never even used any kind of dialog in my games so far. but i checked your .cap and i thought i could atleast give a small hint:
use event groups. not sure if theres any glaring bugs involved with them, but i havent run into any myself. they help you keep the event list tidy and well organized. also helps with pinpointing problems if / WHEN you encounter one. also, commenting your events is pretty useful too, incase you forget how to do stuff and just helps you keep track of what does what. you can access those when you click right mouse button while you're on event sheet editor.
sorry if this was pretty vague, but since im not an expert, i see no big issues with that .cap.it would probs be a ood idea to first make a "messy" game, no matter how broken and buggy. then just start from scratch,when you have some kind of an idea what lies ahead, you could probably make a more clean and more organized game after that. atleast thats how its been for me. every new .cap is cleaner and better performing than the last.
i could say just download lots of examples and .caps lying around here, there's alot of neat tricks and tips in them. also, this section of the forums is a goldmine, when you eventually run into problems, so use the search function like there's no tomorrow!
that's my two/three cents. just hang in there and try out stuff.