So how would you start out using your realm points?

Purge first! Then mana actives if you find yourself out of mana often (MCL, RP), otherwise go for cast speed abilities (ACU3+MOTA2 I would say). Passives to raise your damage later on in your realm rank.

mcl1 is a mana boost every 5min for only 3 pts, so get it asap, ideally already for levelling. RP (incl. the pre-requisite MCL2) is stupidly expensive, i would at max get mcl2 alone.

mcl1, dex1, acuity2, ser1, acuity3, mota1&2, (mcl2 if ure not using pom/power pots)

then think of WP and MoM to increase dmg, and if u use ur debuffs a lot WA1 isnt bad either.

i wouldnt spend all those spec points on purge at RR2. it's imo 1)cast speed and 2)mana. Then at >RR3 you can 3) get more dmg/debuff crits/ even more cast speed.
And THEN think if u wanna trade in half of the stuff that u have for a purge that is a once-in-30min-thing, and if the answear is yes then get a stone and respec for purge.
I personally wouldn't consider purge at all before RR4L5 or sth but that s me.