Chance of Getting In

I am 16 y/o, just finished national 5's and going to apply for St Andrews come end of year with my predicted grades for highers. Im going to apply for financial economics BSc and wondering my chance of success when I apply so I can act accordingly (may need to grind some extracurriculurs during the summer). My extracurriculurs are as follows -> National debate team (1 year), Dundee football club academy (6 years), worked with a professor on an economics paper, bronze junior maths award, (a couple trivial school leadership and participation things such as winning chess tournament etc). I understand apply at the end of s5 will make my applicaton significantly weaker but im just wondering if anyone can shes some light on the chances i have? Much appreciated.