Innates and you

Hey, you, yes, you, the bimbo with the broadsword! Are you a fire user? No? Well, are you a water user? Well, you are!? Great! What's you affinity good sir? Earth? Well that's a good affinity for you. But did you know that Water is one of the most difficult Innate elements to match with a good Affinity? Why, you ask? Well, i will tell you why. See, you've got earth, which is good and if you are creative then you can make land slides and fissures can open to release geysers with boiling water and steam which can melt away flesh. You can lock in enemies with a muddy grave and what's more, you can hit that with ice afterwards and freeze that enemy stiff. But you other choices are ice. You may as well let an ice user do what they want. You may also wonder why water users can't just use ice. That's because ice and water are so diverse in their properties. No other element has such diverse properties that they need separate signs for their states of matter. Water and Ice are the only two. Now, you may wonder even further why magma is not its own element. That's because using magma would essentially be the same as using fire. it's hot... You set things on fire with it. Aside from that, Fire and Earth are needing to produce magma. This thinking would suggest that you would need water and cold to create ice. Why make cold and element....instead of just ice.

Now, why have we gone through all of this. Just to bring up your innate and your affinity...working together.
We're going to clear up all possible confusion on the subject.

We're going to use Bob and Sammy here.
Bob is a nice Drag'Konin Archer with a bit of a feminine side and Sammy is one pissed of Inple with am Electra complex and a giant ax. Boo hoo for Electra complex...

Bob here, well, his Innate is Fire. His affinity is Earth.
Sammy's Innate is Earth, affinity is Water.

Let's say Bob and Sammy are strolling through Poschter's Pass when a Grantix jumps out to fight them. They both ready themselves for battle and engage in combat with the Grantix. Bob lands the first hit with a regular arrow strike and Sammy follows by slamming his massive sword the monster's chest. Now, when Bob uses an attack named flame wheel and slams his spinning body into the creature, he will leave a small amount of fire enemy lingering around.

This is where the affinity comes in. Sammy's affinity is water. That means that if there is water energy lingering, she can channel that energy and mix her Earth energy into it, creating a new attack that is 2.5 times more powerful that her own attack. The problem, is the fact that Bob has left fire energy lingering. Sammy will ignore this energy and use Chain Pillar. Sammy slams her blade in the earth in front of her and sends a rippling tide of earthen chards smacking into her foe.

Now, we get to see some affinity work. While the attack is still working, (And remember that once you use an element, you cannot post anything that would cause the energy to disperse. Otherwise, your teammate can't use it.) Bob, whose affinity is earth, will use a fire attack. There are three ways to use elemental attacks. You can use a weapon based elemental attack. you would usually just wrap a blade in flames or coat arrows with vines or something to that effect. You can use your Special Skill which, in most cases, with a good lead-in, can kill a weaker enemy in one blow. Or, a Kindler will use elements as weapons.
Bob uses Flame Wheel again. This time, he is free to create a new attack with the earthen energy that is lingering from Sammy's attack. Flames mix in with the towering construct of Earth energy that Sammy released and the attack turns into "Magma Rush" which is the name that Bob's user would "suggest" in his post.

Remember! A GM should also allow elements to linger after a hit. One of us may even say something along the lines of "Sammy's attack struck home but when Bob readied his attack, the crushing wall of rock and debris was still carrying the foe away from them..."
This will signal to the player to use a co-op attack...

Let's say my innate is fire. There are two people in front of me. The character that goes first uses water. The person that goes next, their innate is earth, affinity is water.
Does my affinity being earth, and my innate being fire nullify the water used first?

Yes, you're absolutely right.

To clear it up for other players, in Regalis, there is an invisible atmospheric aura called Aether. All elemental energy lingers on this atmospheric presence and can be drawn by people in the world. When beings are conceived, their bodies pull in elemental energy from the Aether and that becomes their innate. Their affinity comes to be because of their element's ability to match with other elements so just as their innate, they have no choice in the matter.
Say you want to create flames to wrap around you sword. You draw fire energy from the Aether to do so. Areas also have more powerful channeling to the Aether. In a forest, it is easier to make vines erupt from the earth. In a volcanic area, it is easier to draw fire from the Aether but more difficult to draw moisture from the air to form water.
What happens during an elemental attack is that the person that went first would have channeled water and would have used it as an attack. We'll call him Dimitri. The character that went second will be named Austin and your character for Regalis is Oleris. For this, we'll say that he is Fire Innate and has an Earthen Affinity.

When Dimitri performs his attack, he uses a simple burst of water to rocket up from beneath his enemy. We'll also say that the enemy has been officially floated in this post as well.
Next, Austin will attack. With his attack, he releases a wall of earthen energy as jutting spikes. Now, even as Dimitri's attack dies, there is still an abundance of Water energy floating on the Aether. Austin's energy mixes with Dimitri's through affinitive properties. Now, Austin is free to manipulate these elements at his behest. He refers to the attack as Galatine Burst and it involves the earth to erupt upwards, engulfing the foe as a dome of water slams down upon the enemy. Now, the enemy is also effectively grounded.
The Water energy has been expended. Now, all that is left is Earth. This is where you come in. You collapse the earth once more and release a towering construct of magma. Fire is simple, but magma is not possible without the minerals in the earth.

So, there you go. I hope that answers any question you may have about innate and affinitive properties in combat.