If multiple effects modify your hand size, apply them in timestamp order. For example, if you put Necrodominance (an enchantment that says your maximum hand size is five) onto the battlefield and then activate Tamiyo, Seasoned Scholar's last ability, you'll have no maximum hand size. However, if the emblem from Tamiyo, Seasoned Scholar's last ability was created before you put Necrodominance onto the battlefield, your maximum hand size would be five.