That's the base ring. You need a prophecy to upgrade it --
The King's Path -- and then the ring gains an extra effect of 0.4% life regen per endurance charge. With 8 charges and 2 rings that's a lot of regen. The prophecies cost ~11c each.
For flasks, I think the guide called for a divine life, a basalt, a stibnite, a sulphur, and the Lion's Roar you already have. The life one I'd do as seething prefix and either heat or staunching suffix. Whichever suffix you don't get there needs to go on one of the others, along with a warding. Prefixes on the others don't matter too much; experimenter's, chemist's, ample, and perpetual are all pretty good. The important thing is to remember that alterations aren't free, so don't go completely nuts trying to roll perfect flasks. I always do a search on poeapp.com before I try rolling a particular flask just to see if someone else is selling one for a really low price.