How do you phrase something unless it is taking in action

Hi there,

Let's say there is a project that a group of people join and it's about to start. The project is for managing a community web site for a program. Somebody in the group says to start from a small thing like updating the web site so that we can see actual problems which can be found only when the project is taken in action. Somebody else says we should not start anything unless the contents of the program becomes more solid.

The underlined sentence is the part I'm not sure about whether what I meant is interpreted to the reader. I'd like to mean there are some things that are realized only you practice rather than imagine.

Could you rephrase it if possible? How do you say it in English?

Also please correct my English sentences in the question. Thanks.