Hey there.
The most important thing for a cleric is the Heal skill. You'll be using this some uncountable number of times throughout your clerical life, so a "must-do" thing is to put 5 points into the cooldown.
5 points into SP consumption isn't a must, but it's very useful, and cuts down a lot on your SP stone/pot usage.
5 points into power is also good, but for me atleast, it's not a priority at the lower levels.
Then comes Bash, which will be your only meaningful attacking skill for a long time. 5 points into power, and if you solo a lot, you can consider putting 5 into either of CD time or SP cost.
Then, the level 20 skill Invincible. 5 points into duration for this skill which takes it up from a 10s effect to a 17.5s effect.
Here, check out
the wiki for some great info regarding the game (and if you can help update it, that's also great
); and more specifically, here's the info on
Cleric Skills. There you can check out all the skills you'll possibly get, and can see what each improvement does to them. Also check out our
Guides forum where there are lots of cool guides, not only for clerics, but general guides too.