The /g/ sound is spelled with <g> throughout. The /j/ sound is spelled <y> and is the unwritten glide before <u> in use.
The contrast only occurs initially in a small number of words, and is between a velar stop and a palatal semivowel, both voiced. In spite of the closeness of the tongue position, it does not cause any problems.
gait Yate gall yawl galls yawls gamma yammer gammas yammers gap yap gaps yaps gapped yapped gate Yate gaud yawed Gaul yawl Gauls yawls gauze yaws gawk York gay yea gays yeas gear year gears years geld yelled get yet ghee ye gob yob gobs yobs goo you Goole you'll goose use gore yaw gores yaws gored yawed gore yore gore your gores yours got yacht guard yard guards yards guess yes guesses yeses