bard use a lot of different ability scores, so they're tough to do well on a low point buy...
if you're allowed to take Aasimar, that'll help- Musetouched get +2 Dex and Cha with no penalties. look at the Spellsong feat, it lets you hide spells if you cast them with bardic music.
I suggest going pure caster bard. Spell focus nec g spellfocus nec spellfocus illusion g spellfocus illusion.
Then focus on fear spells wether illusion or necromancy. For this I recomend either normal gnome or dread gnome.
To avoid spellcasting detection thete is a bard feat that mixes the performance making actual spellcasting hard to detect.
But basically play like a narrowly focused necro debuffer or illusionist.
One caveat though is while I'm doing this very build in carrion crown my char is only lvl 6.