When should i wash my hair?

I'm trying to figure out when i should wash my hair. In 7th grade i used to wash it every day. Now i used to wash it every other day switching between head and shoulders ( i got dandruff) suave for men and some Pantene shampoo ( eh they were on the bathtub so i used them all). Then i did it every 2 days. It still was too dry so i waited a week. it looked fine but it seemed kinda unclean to me 0_o. So when should i wash my hair and should i switch shampoo? ( i'm kinda west indian if that helps and my hair's long) Oh and my mom bought some Sunsilk shampoo+ conditioner for dry and damaged hair ( i don't use conditioner) so ... ugh yeah 0_o