Cheap first car or save?

Hey everyone, I'm an 18 year old looking to purchase a first car sometime soon. I'm a full time uni student doing casual work. During the semester, I earn about $350 per week but will earn about $600-700 during breaks. I am living with my parents so my biggest debt is my girlfriend 😅. I've got about $15k saved up right now. I'm big into the 4x4 scene and was wondering if I should buy a car right now or save for a nicer one in 12-18 months time. Thanks :)