Destiny 2 general guide *IMPORTANT*

Different mods can only be found for specific pieces of armor so first the list and then how you should build your character.

Arc Grenade Cooldown - Chest and Legs
Arc Melee Cooldown - Helmet and Gauntlets
Arc Class Ability Cooldown - Gauntlets, Chest, and Titan Class Item

Solar Grenade Cooldown - Helmet and Legs
Solar Melee Cooldown - Chest and Legs
Solar Class Ability Cooldown - Helmet, Legs, and Warlock Class Item

Void Grenade Cooldown - Helmet and Gauntlets
Void Melee Cooldown - Gauntlets and Legs
Void Class Ability Cooldown - Helmet, Chest, and Hunter Class Item

Kinetic Weapon Reload Speed - Gauntlets and Titan Class Item
Kinetic Weapon Recoil Reduction - Chest and Hunter Class Item

Power Weapon Reload Speed - Chest and Titan Class Item
Power Weapon Handling - Chest and Warlock Class Item

Energy Weapon Handling - Helmet and Warlock Class Item
Energy Weapon Recoil Reduction - Gauntlets and Hunter class Item

Resilience - Helmet and Titan Class Item
Recovery - Legs and Warlock Class Item
Mobility - Gauntlets and Hunter Class Item

Resilience, Recovery and Mobility cap at 10 so anything above that has no effect whatsoever so you should never modify your armor in such a way that you go over those caps, the selectable traits will help you adjust your stats accordingly if you switch pieces of armor occasionally such as swapping your exotic armor a little.

Reload Speed only really has any impact on weapons with an already poor reload speed and even then it's not terribly efficient so unless you have some of the slowest reload times in the game you're better off taking either armor boosts or possibly a cooldown.

Handling has negligible benefits across the board whether a weapon has good or poor handling you won't notice a difference unless you slow down the game and compare them side by side for general gameplay prettymuch everything else will have a larger impact.

Recoil only benefits horizontal recoil so any weapon with vertical recoil will be more or less unaffected by this trait so you can't turn a vertical recoil pulse rifle into a steady weapon magically and since this is the only way outside adjusting stability to even impact recoil, what you see is what you get with vertical recoiling guns, but horizontal recoil weapons can be reigned it a decent bit so your high impact, high recoil guns may get some benefit from recoil reduction provided they have a high enough firerate that you might not be able to adjust fully before the next shot is ready.

For the cooldown reduction you have to look at the actual cooldown timers to judge whether or not it's worth it to you to reduce your cooldown over simply improving your base stats in most cases since base stats are persistent and even with maxed cooldown you're abilities have substantial downtime they're not worth reducing, but each sub-class has something they excel in so maybe it's worth reducing something like the Nightstalker's Void Grenades for territorial control or the Sentinel's Melee to help keep Defensive Strike going as well as add power to your Melee to get some healing in or possibly the Warlock's Class Ability if you want to play a more Cleric-like character.

*All cooldown times are in Minute.Second format*
Melee Cooldown Times
Arc Warlock - 1.36 > 1.28 > 1.20
Arc Titan - 1.23 > 1.15 > 1.09
Arc Hunter - 1.36 > 1.28 > 1.20
Void Warlock - 1.23 > 1.15 > 1.09
Void Titan - 1.23 > 1.15 > 1.09
Void Hunter - 1.36 > 1.28 > 1.20
Solar Warlock - 1.23 > 1.15 > 1.09
Solar Titan - 1.23 > 1.15 > 1.09
Solar Hunter - 1.36 > 1.28 > 1.20

Grenade Cooldown Times
Arc Warlock - 1.23 > 1.15 > 1.09
Arc Titan - 1.23 > 1.15 > 1.09
Arc Hunter - 1.23 > 1.15 > 1.09
Void Warlock - 1.23 > 1.15 > 1.09
Void Titan - 1.23 > 1.15 > 1.09
Void Hunter - 1.23 > 1.15 > 1.09
Solar Warlock - 1.23 > 1.15 > 1.09
Solar Titan - 1.23 > 1.15 > 1.09
Solar Hunter - 1.23 > 1.15 > 1.09
There are two exceptions to Grenade Cooldown Times which are the Arcbolt and Firebolt Grenades which follow a 1.00 > .55 > .52 cooldown.
Class Ability Cooldown Times
Arc Warlock - 1.23 > 1.15 > 1.09
Arc Titan - .38 > .35 > .31 > .29
Arc Hunter - .24 > .22 > .20
Void Warlock - 1.23 > 1.15 > 1.09
Void Titan - .38 > .35 > .31
Void Hunter - .24 > .22 > .20 > .18
Solar Warlock - 1.23 > 1.15 > 1.09 > 1.04
Solar Titan - .38 > .35 > .31
Solar Hunter - .24 > .22 > .20

As you can see even maxing your cooldown times doesn't shave too terribly much off the respective times so it's best to stick to one item your character is particular good at and focus on reducing it's cooldown if you want to reduce your cooldowns at all to avoid your base stats from taking too much of a hit from not being boosted by mods.

Resilience Health Estimates
0 = 186
1 = 188
2 = 190
3 = 192
4 = 194
5 = 196
6 = 197
7 = 198
8 = 199
9 = 200
10 = 201

As you can see Resilience barely increases your health, these are purely estimates done via testing in the Crucible, what Resilience is good for is potentially helping you survive one additional bullet against slow firing weapons. The MIDA Multi-Tool right now is the top of PvP meta and to get an extra hit against it you want 4 Resilience, but this only factors in an additional body shot once your shield is broken in PvP.

Mobility does not affect sprint speed, it only affects jump height and walking speed this however does incorporate strafing speed when hard aiming so it can help you dodge bullets whilst returning fire making it a solid stat to roll for.

Recovery helps you heal up if you have a much higher Recovery in the Crucible you can get back in the fight faster or simply heal faster than your opponent and have a life advantage after you heal significantly more health in the same amount of time as it takes them to heal, but mostly it's about post engagement healing to keep you healthy. Healing time is also significant in PvE so you spend less time cowering behind that tiny rock clinging to dear life or you might even be able to fully heal between waves of enemies if your Recovery happens to be high enough.

Recovery is tricky since it's a rate, but at the time it takes for a level 10 to fully recover levels 1-3 are still in critical health which is max critical health is a pausing point for recovery so Recovery Level 4 is the point where you're past the pause for Critical Health when a level 10 Recovery would be a max health. The most notable leap in Recovery is from 9 to 10 where a Recovery 9 is missing about 25% of their health still when a level 10 would be maxed.

Rough Percentage Health at the point when Recovery 10 would be full.
10 = 100
9 = 75
8 = 66
7 = 50
6 = 40
5 = 35
4 = 30
3 = 25
2 = 25
1 = 25
0 = 25
*Do note that 25% is the Critical Health Cap so Rates 1-3 are all at the paused point of max Critical Health where Rate 4 has passed it, also note that while the gaps looks large the gap for recovery 9 to reach max health is only about 1 second longer than the next one up as a general rule.