Ok so like.
The Grey Warden “tabard” is a full body scale-mail “shirt” fastened at Mordred’s either sides. Under that he wears something like Blackwall’s aketon but thinner, because he doesn’t expect to wear full plate armor + the tabard is already backed by dyed-blue leather, so the chafing isn’t so bad.
Cape n shit afterwards. On his belt are pouches for spell ingredients (some of his magic need them; he learned the “wilder ways” from Chasind shamans and Dalish mages), vials upon vials of mana potions, a number of other things, and the sword. Shield he doesn’t lug around while traveling. Mordred actually uses a longsword that lets him either two-hand or one-hand effectively, and he’s agile enough to parry/evade foes rather than just turtle his way through assaults. It’s not until Inquisition that he picks up a shield again.
He’d look like bona fide Grey Warden traveling if it hadn’t been for the BIG FUCKING CAPE that’s ROYAL BLUE (an expensive dye to find and also even more expensive to buy that much dye to make that much cape; Leliana’s budget thanked Mordred for being small), GLITTERING from all the enchantments he sewed into it…