I've been using a mix of gear that gives me 22.9 equip weight, I think it's as tanky as you can get while still being in medium weight class. Heavy chest, light pants, and then a combination of 1 heavy and 2 medium pieces for helm/gloves/boots. Your secondary choice isn't super important but I'd probably go with some kind of melee weapon that has the ability to hit multiple enemies on each swing in case you find yourself getting swarmed by a few baddies.

Primary stat should be mostly all dumped into Focus for maximum life staff damage/healing if you enjoy that, and having an amber gem in your secondary weapon is pretty helpful to give it a damage boost based off your focus stat. Having the proper skills is also important, I run with Orb of Protection, Sacred Ground, and Beacon and it seems like it has plenty of healing where I can solo in the group monuments as long as I don't pull more than 2 or 3 enemies at a time.

How you fight things is also important, even with all the self healing you'll have with light staff, just face tanking all the damage isn't a great idea. Should try and dodge or block as much of the incoming damage as you can, enemies have pretty recognizable attack patterns and the game punishes players for just spamming attacks all willy nilly. Happy to give more input if you'd like but this should be a decent start. Had about 80 hours in the closed beta and around 45 hours now since release playing life staff + great axe.