HN user
I love programming, and code mostly in PHP
Tough one. One option is to use a poll. The best option is to go with your opinion, and that of your fellow founders. If you think a feature would make a good addition to your software, go for it. If the feature takes away from what your project is, don't use it.
"I use "Project Management" or "Planner" available in Ubuntu's repositories."
Same as me. Free, and easy.
I recommend PHP, and SQL, using MySQL/PHP/Apache/Linux. For an editor, I recommend Bluefish. After that, go with Perl(Old style, but it has it's uses) and then Python. Ruby is the next step after that. W3Schools is a good place to start learning, but the best way to learn is by doing.
quit your job if you have one, and tell everyone you know about your startup and how you will make thousands/millions soon.