Take note of the reply above about not spending too much time on a framework / tools/ engine.
Then remove the word 'tools' from it!
While it may be easy to spent way too much time on a well-engineered engine or over-ambitious tech-for-techs-sake, you really don't want to underestimate the importance of decent tools.
They don't have to be high-tech or optimized - but they need to be stable and very usable. Especially if you're making a game that needs a decent amount of content, or where level design is key.
And especially if you're working on a team of more than one. If your level-building tool sucks, even the best artists/designers out there will struggle to build good levels.