If the issue is the lack of sponsorship, you have a bigger problem. Obviously, you need to find a sponsor. Cand understanding what is important to each of them. Your company s leadership has an obvious stake in the successful completion of the project, but don t overlook external stakeholders, such as customers or vendors. So, be prepared to answer.
Work frequently needs to be redone, and progress comes in fits and starts.
There are no specifications. Without either, warnings will be going off like alarms in a burning building. A mess of this sort typically starts because of pressure to complete the job. Unless you pull over and wipe off the mud, there is going to be a wreck. Both you and the team need a road map, and you will need to be able to gauge your progress individually and as a group.