As a wizard you will have Wizard attacks and Cleric buffs.
So you will attack with your staff.
But if your hp becomes low, you go to your cleric rod and make heal skill.
For example healing cycle for decent hp over 16sec.
But also healing favor or other healing skills can be used to regain hp very fast. (Group recovery is my favorite).
Also these skills heal 9 out of 10 enough with a level 32 cleric or lower.
Because once you switch to wizard, the magical attack of the wizard staff is taken for healing.

So if you use healing cycle (And recovery division on level 40) you can even do it with level 1 cleric rod.
Only if you use skills as group healing / healing favor , then a high cleric rod is needed.
(Please note that these skills consume a lot of sp ;P)
I will put a small list of must have cleric skills:
Row 3: Faith (Passive)
Needed for your healing skills.
Row 4: Absolute damage (Dont skill for now, but on high level usefull in pvp.)
Row 5: All skills.
The cycle and orbit are best in my opinion. Even though the others will heal you very fast, but for a short time.
Row 6: Bless spell!!! Recovery division!! (Holy recovery division on level 90)
Bless spell, 45sec of insane defense. Almost impossible to die with bless spell on.
Recovery division, this buf stays for 5minuts, and heals you ever 2-3secs a certain ammount.
Row 7: Ressurection skills.
Usefull if you are in parties. These skills can be used on other players to make them alive again.
Row 8: Glory passives. If you wear light armor (which you should!) these are very nice.
As soon as you switch to cleric your defense get boosed a lot by these skills.
Row 9: Offering
Funny to do against low lvl uniques, insane damage, but 95% hp will be consumed.
Only do it against things you are 100% sure you will kill. Otherwise it will kill you!
Row 10: Holy word / Holy spell
This helps you not to get burned / poisoned or other bad effects. so get it.
Row 11: Blessings
Usefull only if you plan to stay cleric in a party. It can increase the STR INT stats of other party members and there phy and mag defense. But when you switch to wizard, all buffs will be gone.