I've always wondered about the yellow runes for it;s 0.25 gold/ 10 sec is it really worth it since it only give like 2 gold every 10 sec and then again it uses 9 rune slots although there isn't much u can use there if u play ap,...anyone can help plz?

Arnor is a good choice early on to help mitigate creep damage and jungle pressure, health per level and flat mana or mana per level are also solid choices. Magic resist was recently nerfed, but still a solid choice vrs AP assassins such as leblanc or veigar. Gold runes make a pretty small difference overall, many support players and such started to opt for flat armor or movespeed to help aid or escape ganks better, and the additionally survivability.