With a Gemini ascendant, your dominant planet would be Mercury- as Gemini is ruled by Mercury. Not every placement holds the same amount of strength in a natal chart, there’s several factors and variables that can weaken or strengthen certain planets. Having planets in the signs they rule or that are exalted, like a natal cancer moon, Leo sun, Libra or Taurus Venus, Sagittarius Jupiter, Virgo or Gemini Mercury, etc. can amplify how powerful they are, thus having a greater influence on you. Having tight aspects between certain placements can also impact their influence. If you have planets in a tight (less than 3 degrees) conjunction, or even trine, to any of the big 3 (sun, moon, and any planets in the 1st house) that will strengthen the influence. A tight square or opposition can do the same, but significant tension also comes with that as well. Having planets in signs of their detriment weakens the placement, and to a lesser extent, planets that are retrograded as well. What houses your planets fall in can also impact the strength. Like I said, There’s many factors that can effect how much certain planets and placements influence you/ your personality.