Hello guys. I am new to this website. But what's the best armor/weapon that can be bought for a Sith Warrior?

Anything orange. Then you can swap mods and ect.

Whatever you think looks good use, just as long as you can upgrade the hilt/armoring/mods/enhancements as you level. Those are what makes your gear good.

Also augmenting your gear.

well it depends on what your trying to do in the swtor world you generally don't buy the strong items like they said, find a orange that u like the way it looks as long as its fully modable well orange or purple, don't forget to augment it, and to get the mods either flash point if your going to pve, or pvp

Also depends on the level... As a warrior you want strenght and endurance on your stat.
Then a mix of power, critical rating, surge rating, and accuracy.
But as they said, once you level up, you should just take an armor you find good looking, ( you will be able to change the mods from an armor to an other anyway, if you prefer an other armor for exemple)
and mod it with new mods as you level, mostly from quests and planetary commendations
when you reach high levels, you will get the mods from the gear you get that can be bought with commendations ( classic, elite, warzone commendations etc).