"Since we were 3 business people, we spent all this time into idiot plans, budget forecasts, BUSINESS CARDS, fancy website… all useless things which in the end did not contribute to anything."

I've been apart of a lot of startups and this is far and away the best advice. It was a common theme with two startups I worked for during the boom years. One CEO's hubris was stunning. 10 million privately funded and he blew most of it on season tickets and suits at stadiums to "entertain" big prospects (nevermind we didn't have any "big" prospects at the time!), remodeled the office to the tune of a few hundred thousand dollars, it goes on, but you get the idea.

When you're in a startup, it really is about getting your product shipped, and making sure that's where the focus is.

Great writeup and glad you saw the errors of your ways. Lots of people never gain the wisdom you have until after two or three failed attempts.