Recommended skill ranks in discipline?

[jeremiah]

Just got the Diamond compilation of NWN. Created a pal1/sorc3 character at the moment clearing out the streets of Beggar's District and Peninsula District.

Rod of frost, burning hands and mage armor was enough for most of the prisoner fights on the streets and houses. Lured some to the gate guards when it got too tough (trying not to use henchmen) and try to get the finishing blow to get the XP. Magic missile and acid splash taking care of the weak zombies.

Need suggestions on Discipline as would prefer to avoid knockdowns for this character. Currently have 5 skill ranks (maxed it when taking 2nd character level as paladin). Managed to get a gauntlets of discpline (+2 or was it 3 to discipline). Should I need to put more skill points into this or just hope for better items that give discipline bonus and/or cast bull's strength (as I understand strength plays a factor with the dice rolls to prevent knockdowns).

If so, was hoping to put points into tumble (cross class) as attacks of opportunity when casting, and surrounded or moving is pretty common at the moment. Concentration and spellcraft always maxed (12 intelligence human)