Play demon avenger. Great class, at the very least the level 2 link will help you and a good start to your legion, and doesn't use many pots.
Gather as many of the boss set items as you can (Zakum accessories, horntail ring/earring...) and scroll them for hp. You'll be able to replace these easily so no worries.
Save up money to buy reinforced pendant and belt. Not sure if their prices have gone up since the 25* update though. The set effects give 1200 hp, and again they are something you can scroll for hp.
Get a Dawn warrior to level 150 and Mihile to level 140, and if you feel like it, 140 dark knight. The first two give flat hp and DK gives %hp.
Work on unlocking pocket items by getting level 30 charm through horntail pendants, Zakum helmets etc and get a pink bean pocket flamed for hp.
When you find an elite boss or the item dropping rune effect, find any epic equips (preferably 3 lines) and then transfer hammer them to your CRA equips and occult cube for %stat or hp.
At 160, try hunting for someone 160-170 who is interested in trying Kenta PQ. At 160 it gives 30% per clear (5 mins with no idea, but my record is 2 minutes 47 seconds). The bosses drop a small amount of potions and gives you charm accessories. And good exp.
Join a guild if you haven't already. Generally useful to join an active one.
I remember starting a new account (phantom) 13 months ago and the squishyness is awful, but it gets better and after level 200 your hp is mostly irrelevant as mobs will hit 1s on you where you train.