Dominic's outfit needs to reflect his "Ultimate Dumb Outgoing Runner" title, balancing athletic wear with a slightly goofy, unrefined aesthetic. We'll avoid anything too sleek or professional, opting for a look that suggests enthusiastic participation rather than meticulous planning.

Top: A brightly colored, slightly oversized running singlet or tank top. Think neon orange, electric blue, or even a clashing pattern like lime green and hot pink. The singlet should be slightly too big, hinting at a lack of attention to detail in choosing the right size. It could have a small, slightly faded sponsor logo – perhaps for a local bakery or a completely nonsensical company.

Bottoms: Baggy, slightly too-long running shorts in a contrasting color to the singlet. These shorts could be a slightly faded color, showing signs of wear and tear from numerous runs. They might have a slightly different length on each leg, further emphasizing the haphazard nature of his attire. Consider a slightly visible, mismatched pair of athletic compression shorts underneath.

Shoes: Well-worn, brightly colored running shoes, possibly with mismatched laces or one lace missing entirely. The shoes should show signs of wear and tear, with scuff marks and dirt indicating frequent use. The brand could be a budget-friendly, less-known brand, further emphasizing his lack of focus on high-end equipment.

Accessories: A sweatband, possibly slightly askew or too tight, in a clashing color. A brightly colored, slightly oversized water bottle with a silly sticker or two attached. Perhaps a slightly ripped or faded running cap, worn backwards, with the logo barely visible. Consider adding a quirky, oversized wristband or two in mismatched colors. A small, slightly damaged MP3 player clipped to his shorts would add to the overall "dumb but enthusiastic" vibe.

Overall Impression: The outfit should be comfortable and practical for running, but with a clear lack of coordination and attention to detail. The colors should be bright and clashing, the clothes slightly oversized and worn, and the accessories quirky and slightly haphazard. The overall effect should be one of enthusiastic, slightly clumsy energy, perfectly reflecting Dominic's "Ultimate Dumb Outgoing Runner" title.