Fire (Aries, Leo, Sagittarius) + Air (Gemini, Libra, Aquarius) are good matches because the air is the fuel to fire.

Earth (Taurus, Virgo, Capricorn) + Water (Cancer, Scorpio, Pisces) are good matches because water nourishes the earth.

Fire + Water generally do not go well together because both signs are overly emotional and are driven by the heart.

Air + Earth generally do not go well together because both signs tend to be reserved and are driven by the head.

Raw vs Elemental

I get a ton of questions asking me if elemental or raw should be the focus for a certain weapon.

If the gap is large go raw every time. If one weapon is slightly lower but has the right element, and you know what parts to attack, use that.

Damage calculation will tell you which is best (http://gaijinhunter.tumblr.com/post/73946102476/mh4-how-damage-calculation-works-simplified). After sharpness bonus and such is applied imagine your weapon is raw base of 250, and you did an attack with a motion value of 20 to a head that is 65% damage, that would be around 32 damage. If you had element of 300 and the head was 30% weak to it that is like 10 damage. Consider how many hits you are doing (SnS and DS and even Glaive to an extent you can have a larger gap in raw and do more damage), but also realize if you hit the wrong part with element what was 10 damage can be 5 or even 0.

Most of all have fun. Choose weapons you enjoy and like the design for. Nothing is better than enjoying a weapon you worked hard to make even if there is another weapon that is a little better.