Overview on Gear Upgrading in Onslaught
With the release of Onslaught, gearing has fundamentally changed in SW:TOR. Gear drops are now based on your equipped Item Rating (iRating) and scale when completing all content.
All bosses in Flash Points and Operations now drop around 2-4 pieces of gear that are similar or better to what you currently have equipped. This allows for a faster acquisition of relevant loot.
All loot is now Legacy Bound as well, meaning you are free to share gear among your various characters.
Disassembling loot will grant you a small amount of Tech Fragments, which are also looted from bosses or granted from conquest, daily, weekly, PvP, and GSF missions. You have a cap of 10,000 at any time, with the most expensive things currently costing 3,000 fragments from your class vendor in the Supply Section on Fleet.
Note: They only sell "Shells" which you will need to equip with mods you loot elsewhere, or purchase from the SoW vendor.
Gear pieces and their various enhancements now also have "Amplifiers" which grant minor stat boosts to nearly everything in the game, allowing you a great customization on how your character is equipped.
Recommended Gearing Path
Currently, the fastest way to up your iRating is running a Master Mode Hammer Station or Red Reaper due to their ease of difficulty and quick completion time.
Completing the Onderon Daily every day will grant you 100 tech fragments and a gear box.
Completing each Mek-sha heroic every day will grant you 100 tech fragments and a gear box (200 and 2 boxes total).
Completing the Onderon Weekly will grant you 400 tech fragments and a large gear box, once per character per week.
Completing your personal Conquest will grant you 100 tech fragments and a small conquest gear box (1 random set piece), once per character per week.
Completing Guild Conquest will grant you an amplified version of your personal Conquest goal based on invasion tier. (large grants 3 random set pieces, for 4 total per character per week)
Winning a PvP match will grant you 100 tech fragments and a Warzone Gear Box.
Winning a GSF match will grant you 100 tech fragments and a Ranked Warzone Gear Box.
Completing the GSF daily will grant you 400 tech fragments, a gear box, and Processed Isotope Stabilizers.
Completing the GSF weekly will grant you 700 tech fragments, a gear box, and 50 Processed Isotope Stabilizers.
... and many more to come.
Regardless of what you do, always equip the next upgrade otherwise your iRating won't increase which means you won't get better loot. Don't stress about gearing, because as you can see, there are TONS of ways to obtain gear.
However, Conquest and PvP COMBINED are the best way to get crafting materials for the new Augments. FPs and Ops do grant small amounts of Processed Isotope Stabilizers, but nothing compared to the rate PvP hands them out. Conquest is the only way to obtain the Solid Resource Matrix needed to craft augments for your new gear.
The Road to 306
So we covered how to actually purchase gear and all the things that earn rewards.
Actually getting to 306, you want to do so as quickly as possible. Currently, running Master Mode Hammer Station provides the fastest loot times.
What you will want to do is avoid messing with mods/enhancements/armorings.
Simply equip a higher iRating item as soon as you get it.
Once you get to 306, the Vendor on fleet will always yield 306 gear relevant to your spec. That is where you will spend the majority of your tech fragments after purchasing/looting/earning set bonus gear and tacticals.
SERIOUSLY - DON'T WORRY ABOUT STATS AS YOU RISE TO 306! It's so easy to get perfect stats for your class once you reach it!