It is all a function of
- the types of colleges you hope to apply to (the top tier colleges will want to see the guidance counselor check the box on the recommendation saying you have taken the most rigorous schedule available at your HS);
- what courses your HS offers (are honor classes, APs etc, available to sophomores in your HS?); and
- what level of work you can handle. How are you doing in your current classes? You want to challenge yourself but not get in over your head.
IMO the best people to get advice from will be your current teachers and your HS guidance counselor who should have the best understanding of your abilities and the offerings at your particular HS.