First of all, the Bible is a great source to pull from. I'd even say that it's the most reliable ancient text ever discovered. We have discovered tens of thousands of Bibles that originate from only a hundred or so years from when Jesus supposedly walked the Earth. Compare that to sources that are more widely accepted as historical proof (such as Herodotus' Histories) that have only a few copies, or in some cases only exist in copies made a thousand years after they were supposedly written.
Outside of the Bible, there are also extra-biblical sources that depict Jesus and point to the validity of Christianity. A piece of graffiti discovered in Rome that was meant to blaspheme Jesus points to his divinity in an ironic twist of fate. Made at around 200 AD, the Alexamenos graffito shows Jesus on the cross with a donkey's head, with the inscription "Alexamenos worships his god" in Ancient Greek. This is to poke fun at the artist's friend or perhaps enemy named Alexamenos, who apparently was a Christian.