Complex sentence: Born in Aylesbury, England, Gray started his career at Wycombe Wanderers before joining Crystal Palace when he was fifteen, after Wycombe Wanderers closed their academies at the start of the 2012/13 season.
Split into simpler sentences: Born in Aylesbury, England, Gray started his academy at Wycombe Wanderers before joining Crystal Palace when he was fifteen. This came after Wycombe Wanderers closed their academies at the start of the 2012/13 season.