Owh, that's a hard decision. Math Addmath and Account was some of the most useful subjects after you've graduated SPM if you're find a work with it.

Anyway, since you've dropped addmath, no time to regret with it and move on.
You can't do much with a SPM cert nowadays, at least get along a Diploma or Degree.
Because there is tooooooo much people is able to graduate with SPM, the competition is too big.

Not only SPM, most fresh graduates in Diploma might find difficulties to compete with the large number of Degree holder nowadays.

If you have money, the everything is not a problem.
You can study in any field you like as long as you can pay the tuition fee in any private college.
Get a decent recognized degree cert and no one will care about you SPM anymore.