Magical dmg improvement

I play as a fanatic in cloth with scepter+shield. I recognize in pvp situations, my magical damage is ridiculously low (cca. 70-80% dmg absorbed) against a 9-10k+ GS players. My equipment is not too good, i am a casual returner, with T2 and T3 hiram stuffs, 9057 GS with gems. What can I do to improve my dmg against players? Improve equipment faster or choose other gems than magic crit dmg (for example magic def pen)?
Thank you in advance for your reply!