Brock - Pewter Gym leader, campfire cook extraordinaire, and would-be ladies' man. Brock is a down-to-earth type of person, so this is a practical look, perfect for a full day of classes or fieldwork.
The basics: This is designed for a warm climate. Opt for natural fibres like cotton, as they breathe better than synthetics, and pack a parka in case of inclement weather. This also give you stacks more pockets - practicality! Sand-shoes are casual-cool and comfortable if you're walking from one side of campus to the other.
Colours: I've chosen a colour palette of mostly neutrals and greys, as Pewter City is known as 'The Stone Grey City'. By keeping to only a few shades it's easier to look pulled-together and fashionable. Brock himself likes to mix it up a bit, though, so don't be afraid of adding some colour, like this pumpkin t-shirt. If you're also a failed-romance waiting to happen, or you just want to express your fandom, try something like this bleeding-heart t-shirt, in breathable and soft viscose.
Accesories: Brock isn't really a fancy jewellery type of person, so I've kept accessories minimal - basically sunnies and a rucksack. If you do go the jewellery route, maybe take inspiration from the Boulder Badge: simple, geometric, silver or grey, and stone. The pendant necklace is a subtle reference. Alternatively - see those earrings? They're little bats! They have smiles and giant teeth! They're so cute! They also look a little bit like Brock's Zubat, which is cool, and referential, without making your teachers think you're not serious about your studies.
Let me know what you think!