in all of my ff9 games (except my excalibur 2 one), i hav always powered up zidane's thievery to 9999. u can first get angel bless in disc 3 in alexandria synthesis shop. then a bit later u go to the card tournament in treno. i usually go out of treno (or outside dali) and start stealing from the monsters. it usually takes around 6 hours. but it's worth it... 9999 damage for 8mp!
if u can't be bothered doing this, just think about me. in my LV1 game i cudn't kill the monsters (or else i'll gain EXP) so i had to steal from the monsters then run!