How many ancient European tribes were there?

Nobody knows for certain. Seeing as how none of the tribes kept any records, we have only been able to identify tribes by family stories. However, due to confusion in lineage, and taking into account that some stories may be just that - stories, even those numbers are questionable. Estimates run from a couple dozen, all the way to several hundred. If you really want an answer to that question, you may want to search "How do I build a time machine?" first.