first of all i think its really cool that you like reptiles at 13, i got my first tokay gecko when i was 4 and now im 22and breed/keep all kinds of stuff

to semi answer your question males usually have larger heads and frills, but im pretty sure they dont reach sexual maturity till about 18 months to 2 years, it can be qutie difficult to sex any lizard and you almost need a male and female next to each other to tell about the buldges especially at a young age, hope i have helped atleast alittle