Test Drive Unlimited Solar Crown

Every percent of Hong Kong roads research gives player reputation + every fifth percent an increase of 500 experience, for example 30-34% of roads - 3000 experience, 35-39% - 3500 experience.

Finding Radiant Prizes in the form of player reputation - 1000 experience for each prize found.

Completing/re-completing races - 2500 experience.

Completing tasks is probably the best way to quickly raise your reputation and earn some money, so you shouldn't ignore them, the further you progress, the greater the reward.