The 17-year-old midfielder, who has also had spells with Southampton and Cardiff since leaving the Gunners, will initially play for the Dons’ Under-21 side.
But Toonga already has his sights set on making the first-team breakthrough at Kingsmeadow.
He told the club website: “I am pleased to have signed here because I have seen that young players get a chance. There are some good youngsters here and they were given minutes for the first team last season.
“That makes me feel that there may be a chance for me too. I am looking forward to getting started in pre-season and hopefully pushing on.”