You could potentially go to 65 million B.C. if you want but you are on the current story path and will get their eventually. I love the nonsense of Spekkio!

Note, Spekkio does in fact change his form based on his levels and for each form upgrade he gives you new items when you beat him, so check in on him regularly. Also the Arena of Ages is actually something new introduced in the DS version, it doesn't exist in the original but it is fun anyway.

Yeah, Robo/Freddy technically can't use magic but since he is a Shadow variant, it means many of his skills count towards all four elements. So Shadow Beam is Shadow, Cure Beam is Water, and later he will learn a skill that is fire based and one that is lightning based so he's a really good character for versatility even though his magic stat is pretty low. Also, Dual/Triple Techs which utilize more than one magic are considered Shadow damage, just as magic combined with a physical attack makes the attack that element, so even without using Robo, Marle and Lucca's Dual Techs together equal shadow damage.