Support Skill / Damage Stacking

Hello guys. Learning player here. Im playing a deadeye+tornado shot character and I was omwondering whats the most efficient way to stack dps in this game. For example, Im using Faster Projectiles,but I was looking to change that skill for Added Fire damage Support.Is projectile Speed that necessary compared to damage increase? Also, does Faster projectiles after how fast I can shoot my arrows? Or just the traveling speed?

Usually it will involve stacking various things that are multiplicative together. If you are having trouble figuring out which ones are best and are looking for some help, probably best to check a build guide for your build or load up POB and see what happens to your dps with different combinations or see which supports are listed as highest dps support gems. Keep in mind dps is not always the only important factor.

Checking meta data can also be useful for learning, like POE.ninja, just don't blindly follow it. Doesn't look to me like many people playing similar builds to you are using faster projectiles, i'm not very familiar with the build though. Public profile can also help if your looking for specific advice on your build.

Faster projectiles is mostly for utility rather than raw damage output, but it's a bit more complex than that. There are setups and builds where it can be increasing your damage due to the increased projectile speed. It does also have an increase to damage on the gem. This damage increased is additive with other sources of increased multipliers, where as added fire damage will be multiplicative, but only on your physical damage. I don't see many people using that either. I think most tornado shot builds are using crit to scale and elemental damage. It's dependent on the rest of your build which will be best, which is why I suggest a build guide, and while levelling these might be fine, so depends what part of the game you are in. Crit is harder to get working while levelling.

Up until recently there was a mastery that caused increase to projectile speed to also increase damage, but I think it has been removed. It may still exist somewhere in the game. Proj speed won't alter how rapidly you shoot, for that you will want increase to attack speed. It can alter other properties like how far projectiles travel.