Well as a blade you'll be fighting and casting some spells to disable enemies and buff yourself. So here's a breakdown for ya:
STR: 18; or as low as necessary if you want to buy the belt of strength from the adventurer's mart and rely on that. DEX: 18; no question, this will give you a crucial AC (defense) bonus. CON: 16; for hit points; only warrior classes get benefits from any more than that. INT: 18 or as low as necessary; this will help you memorize new spells and let you learn more spells. However, if you play on normal difficulty, then you won't ever fail to scribe a scroll, and even on core difficulty you can drink potions of genius to raise this stat to 24 before you attempt to scribe scrolls. A minimum of 11 is good for any character due to a certain monster that drains this stat and can instantly kill you if it falls to zero. WIS: 3; pretty useless, will penalize your lore ability (identifies items), which is already penalized by the blade kit, but who cares? Just use the identify spell. CHA: 15; you may think this is important for a bard, but just take the lowest you can. You'll find a ring that sets this to 18 near the beginning of the game.
18/18/16/18/3/15 is 88 points total, which is a reasonable amount to roll for.