take my advice:
1. dont ever escape any battle....try to beat all enemies and get the point(CP) to power up your crystalium.
2. play easy mode
3. always stagger your enemies first by shifting to ( RAV RAV)... using magic can stagger your
enemies even faster(ex: fire,blizzard,thunder,aero)...then when the enemies is in stagger state...quickly shift to ( COM,COM,COM or RAV,COM(if vanille and fang)...
but in eidolen battle ..there is no stagger...so just change into easy mode...i find it very easy to beat the eidolon after changing into easy mode....im now in chapter 11 and the battle is very hard even in easy mode...currently im stuck with the fal'cie boss for 2 days ...ff13 is nightmare to me...but i must finish it before the ff13-2 is released....
i hope this help you and good luck!!