Being a geared tank is never as important as having geared DPS or a geared healer for hard modes (with the exception of the optional boss in Kaon most likely).
As others have said, do the level 50 dailies on Belsavis and Ilum, in particular the heroic missions to get the ilvl 50 epic mods. Also do the pvp dailies and use the pvp commendations to replace your worst pieces of gear. As for the crafted items, definitetly try to obtain two 'Veracity Nano-Optic Response Implant [Mastercraft]' and a 'Veracity Galactic Combat Module [Mastercraft]'. The mastercraft (critted) versions will have an augment slot and are worth the high cost (~100-150k each on my server). Use the artifact (purple) 'Advanced Absorb Augment 22' in the augment slots, the prices on these varies alot but I can get them for around ~20-30k on my server. Since you just hit level 50 you probably don't have heaps of credits to spare, but once you start doing the dailies they'll start rolling in.
Aside from that, if you have biochem already, try making the Rakata Fortitude Stim as soon as possible (though you do need to complete a hard mode to obtain the Biometric Crystal Alloy required). If you have another crewskill I'd highly recommend dropping it as soon as you've crafted whatever useful piece it can make (critted rakata belt/bracers for Armormech, and critted moddable blaster rifle for Armstech).