Getting OP-1 Catalyst
In my opinion, the easiest way to get that awesome 336 gear is through playing operations. The max level end game gear is 340 (334 for your implants). Being a raider, I encourage that tract. Flash points and conquest grinding can get you to 336, but at lower rarities of gear and will take a much longer time.
Story mode operations reward very little materials. Averaging 15 per run from breaking down the 5 green (uncommon) gear pieces that drop from the various bosses. These green gear items will match whatever item rating you currently have on.
For example, if your boots are 324, and you get boots from a boss clear, you will get 324 boots. Not much progress there.
Instead of using any of this "trash gear", break it down and get the OP-1 materials out of it. Focus on taking out the weekly missions found in the ops raiding consoles on the fleet and scattered around the zones. The story mode operations in the weekly rotation will reward an additional 20 OP-1 materials, effectively doubling the amount of resources you are collecting.
Story mode operations will be your singular source of income, until you get more comfortable raiding. Stick around on the "Fleet" and watch fleet chat for groups forming up and jump in when you see an advertisement. Keep in mind, you need to be a subscriber to join raids and must be at level 80.
Consider joining the "Allies" channel. Type /cjoin allies into the text chat box to join this channel. It is by far the most active LFM channel in the game and can get you into a group of more competent, and more serious raiders (results may vary).
Join a guild. Most guilds raid. Joining a guild, and their discord, will get you a leg up on getting together with like-minded folks.
Your end goal with doing ops, is to be able to get into the easier hard mode raids.
Eternity Vault (EV), Karagga's Palace (KP), Terror from Beyond (TfB), Explosive Conflict (EC) have a relatively straight forward approach and a low learning curve (EC being the hardest of the options). Some raids further up the line have easy bosses, but the final boss can be a bit tricky to a new player. Keep in mind, if you are on a DPS class, you will not be bringing much to the fight at this point. The other 3-4 dps players will be effectively carrying you while you gear and learn the fight. This strategy of playing the easy HMs is harder for new tanks and healers. A seasoned tank and/or healer will need to be there with you to pick up the weight from your lowered stats.
Augments are pretty much 100% a must for Hard Mode raiding. While you are gearing up with the above-mentioned raids, you can defiantly augment your gear to be less of a carry, but this will cost you more augment kits in the long run, which can be a challenge. If you have the support of a guild, or friend, defiantly augment your gear and follow.
The benefit of Hard Mode Raiding
OP-1 Catalyst - point-blank and simple. 15 catalysts from a story mode raid will get you nowhere. An HM raid will yield 75, and an additional 65 if that OP is in the weekly rotation (must pick up the mission) for a full potential of 140 from an HM raid.
You can "bait" purple (Artifact) drops. Simply equip a low level relic (or no relic at all) and you will get relics from every boss. You will use these relics to upgrade to get that sweet 336 gear from the vendor.
Each gear upgrade takes 60-80 OP-1 materials to upgrade, so 1 HM raid can get you a couple upgrades vs a few Story mode runs for 1 upgrade.
If your comfort level is story mode, it is going to take much longer to upgrade you via operations. It may be wiser to use flash points or conquest to level your gear, but you will not be able to unlock the vendor for 336 without at least stepping foot in a HM raid and clearing a few bosses.
Grand total of OP-1 catalysts that you will need varies, but expect to need somewhere on the scale of 2000 to get you where you need to be.