I get the feeling we are back where we started in the first paragraph, but we may advanced slightly. You always face these astrological problems when dealing with the double signs. Thankfully, there are only three: Gemini, Sagittarius and Pisces. Well, maybe you could throw in Libra. There are two sides to any set of Scales.
As for Geminis, they have no traits in common whatsoever, except the fact that each one of them is a double-mirror image, has two or more dispositions and personalities, which he or she can change as naturally and as quickly as you or I can change from swim suits to sweaters on a day when the wind can't make up its mind.
Gemini is Air, Sagittarius is Fire, and the back section of this book will tell you how these two elements mix. Quite superbly, most of the time. Disastrously, at others. But generally speaking, they do get on fairly well. Gemini can incite Sagittarius into action - both negative and positive - that the Archer would never have taken without being stirred by the Twins. Air always fans Fire into higher flames. Sagittarius can make Gemini feel smothered occasionally, because fire burns out the oxygen in the air. But it can also warm it.
This is a 7-7 Sun Sign Pattern, so naturally, each is slightly envious of the other, because each possesses the qualities the other does not have, but would secretly like to cultivate. Gemini needs the Archer's high motivation, ideals, warmth, enthusiasm and sincerity - and needs also the Sagittarian's ability to travel over more terrain mentally, emotionally, geographically - to shoot for a star, and reach it.
Sagittarius longs for the cool poise and charm of Gemini, the talent for keeping the foot out of the mouth, for remaining cool and detached in the face of most disturbing situations, and especially needs the Gemini verbal adroitness, called tact.
When they get together, they have two choices. Each can admire the opposite traits of the other, and try to imitate them, in order to grow and mature spiritually. Or - each can fear and envy the opposite qualities of the other, and try to put them down, robbing each other of all pride in doing his (or her) own thing.
Both Gemini and Sag (pronounced to rhyme with badge) tend to be scintillating, rather than solid - dashing and daring, rather than dependable and enduring. Both have minds capable of high intelligence, but not necessarily designed for achievements of lasting design and construction (unless other planetary configurations in their birth charts give this quality - which, of course, in a number of cases, they do).
The ideas of both are more like shooting stars or comets than steady Suns. What can be accomplished in a few days by Gemini and Sagittarius will often be brilliant, but a project involving longer periods of time and effort may not come off so well, unless there are the just-mentioned supportive planet positions of strength and patience in the nativities. For knocking around together, instant empathy and general compatibility, the glittering Mercury-ruled and the benevolent Jupiter-ruled get along exceedingly well most of the time. But there's always a chance that sly Mercury (Gemini) may be unable to resist tricking sincere Jupiter (Sag) in some way, and the resentment of this may be violent (the Archer being of the Fire Element).
Sagittarians, while excessively emotional at times, are for the most part without guile. The clever, glib Gemini who plays mental chess games with the trusting Archer may later regret the harm done to another human being, however unintentional. According to ancient legends, the gods feel a special affection for these Sagittarian children of the zodiac, watchfully protecting them from those who would harm them. This is the basis for the so-called Jupiter 'luck.' A word to the wise is said to suffice, but not all Geminis are always wise, just clever - sometimes too clever and the Mercury Bird may, when least expected, trip to his (or her) own trap.