Most light sources can't trigger light blindness or sensitivity
Fortunately, the Light Sensitivity and Light Blindness racial traits are triggered specifically by bright light, a specific level of illumination which is explained by the rules about vision and lighting:
In an area of bright light, all characters can see clearly. Some creatures, such as those with light sensitivity and light blindness, take penalties while in areas of bright light. A creature can't use Stealth in an area of bright light unless it is invisible or has cover. Areas of bright light include outside in direct sunshine and inside the area of a daylight spell.
However, "normal" light doesn't trigger light blindness or sensitivity:
Normal light functions just like bright light, but characters with light sensitivity and light blindness do not take penalties. Areas of normal light include underneath a forest canopy during the day, within 20 feet of a torch, and inside the area of a light spell.
Most sources of light (examples of which given on the table at the above link) only produce "normal" lighting, with specific exceptions for spells like daylight, which explicitly produce bright light. When an effect mentions raising or lowering the level of illumination by steps, it is referring to a progression of:
- Bright light
- Normal light
- Dim light
- (bonus extra added by later material) Supernatural darkness
But, if you use something like a torch in an area already well-lit, you don't further increase the light level:
A torch does not increase the light level in normal light or bright light.
Which should probably be extrapolated, if it's not otherwise explicitly stated, for any light source which doesn't normally create bright light - so you shouldn't accidentally trigger light blindness by having too many torches or lanterns.
If your drow is adventuring with a fellow who has low-light vision, that makes no difference to the drow, since unless their friend uses light sources which explicitly cause bright light, they are not at risk of light blindness.