1. naive
2. naif, childlike, wide-eyed, dewy-eyed, simple, credulous, fleeceable, green, gullible, ignorant, inexperienced, innocent, ingenuous, simple-minded, unsophisticated, unworldly, credulous, uninformed, unworldly, callow
3. inexperienced, unsophisticated, immature, unsophisticated
3. artless