1. Collect more evidence: Strengthen the investigation and interrogation of relevant personnel and collect more evidence to prove illegal business practices.

2. Find witnesses: If there are witnesses or insiders, you can contact them and ask if you are willing to provide testimony.

3. Use technical means: use computer technology, data analysis and other methods to find suspicious signs from a large number of transaction records and further determine the facts of illegal business operations.

4. Seek legal evidence: If the evidence is really insufficient, you can seek other legal evidence related to this case, such as checking whether there are illegal financial records or false bills.

5. Consider withdrawing the lawsuit: the evidence is really insufficient, so it is necessary to consider withdrawing the lawsuit temporarily and collect more evidence before filing a lawsuit.