Well, the damage difference of Smite 10 vs. 15 wont be that much anymore by the time you reach Rank 6. You’d have to set priorities, and I believe that honestly just a little more damage ([500-1500]*attribute multiplier]) isn’t worth spending the points unwisely.
But well, you can always buy a skill reset potion later on for 99 TP, so if you’ve got only 1 character I’d just do it and put the points into Smite 15 first.
Restoration should go to level 3 for the sake of the additional SP recovery. 50 additional SP recovery is enough combined with SP recovery from headgears/collections/items to cover a larger portion of your SP costs later on (if you don’t go Kabbalist C1; if you go, you don’t need Restoration at all since Ein Sof will cover your SP recovery and more than double the HP recovered from Heal).
Conversion should at least be lvl 1 because the skill is useful. You have a chance to make monsters inside the circle your allies with every hit, and once converted, they will aid you in battle. There is no reason not to spend at least 1 point here.
Barrier is based on your preference, since lvl 1 will be enough to keep the skill up 100% of the time even with the attribute; increasing is just a boost of 80 mdef that could be gotten elsewhere.
Turn Undead should be lvl 5 or 6 if you can/want to save the points elsewhere, as 9 monsters afaik is the aggro limit for a non-Peltasta character in dungeons. With the current monster amounts on maps, having more is useless outside of maps like Demon Prison 2 with high monster spawn rates and amounts. I also don’t know the exact AoE of the skill, so going any higher seems overkill as long as the killing chance doesn’t scale with skilllevel.
About Inquisitor:
It’s really hard to forsee any changes to the skills at C2, so I’d be careful with leveling God Smash and/or Malleus Maleficarum.
Pears of Anguish is a must max skill, but you have to consider that C2 might bring better scaling alternatives to Malleus and God Smash.
Iron Maiden will surely come (either as C2 or C3, as the developers recent post made it certain to be implemented), and the other possible skills like Iron Boots, Lead Sprayer and Heretics Fork might be worth skilling later on with the points you get…
The safest bet (unless you want to PvP a lot) would be to leave Malleus and God Smash at 1 first, as Breaking Wheel[lvl*2 seconds duration vs 50 seconds CD time] and Pears of Anguish[skilllevel= number of installments] are must-max skills[= skilllevel 15] to be very effective[and supposedly stronger than God Smash and Malleus], and look at C2 first before deciding to spend the rest of the points.
About the 5* gems: don’t sweat it, it’s easy to get them in a few days spent farming in Demon Prison 2. I get like 15-20 2* Red/Yellow/Blue/Green Gems per hour [and more if there are less players], which are equal to ~1,5 4* gems [twelve 2* gems are needed for one 4* gem].
Five 4* gems equal one 5* gem, and by the time you got that, you should have collected enough silver to buy two to three additional 5* gems from the money you’ve made in Demon Prison 2[unless you want to spend it on attributes since we’ve got 20% discount on them and the Heal&Cure damage attributes are worth their money until 80-90%].
I’d advise you to get that 5 slotted 5* red-gemmed Five Hammer,as it will last you well until lvl 315+ when you might want to exchange it with Vienarazis Mace [the recipe was dirt cheap until the introduction of paper cubes, dunno about now].
It will also highly increase the damage of your Heal and Cure skills, which are currently the main sources of my damage, even at Rank 7, thanks to the cheap attributes(currently 1-90% on Heal & Cure costs only about 5 million silver each; that’s about equal to the cost of 70% attribute on Smite and 52% on God Smash), as Heal features two overheat charges per 22 seconds which calculates to, in your case, [(10+1)*2]*2= 44 hits with Blessing+Divine Might.
That’s really nice and makes me strong even without any INT points+ really independent on spamming SP-intensive skills all of the time (you might not need to spam Smite as often e.g. if you can kill your mobs with Heal & Cure thanks to the Five Hammer).
Also, remember that Five Hammer has 5 AoE attack ratio, which will allow you to hit more enemies with God Smash and Smite.
@ last post:
Paladin 3 is basically good because of Conviction. Monsters struck by Conviction will recieve additional damage by God Smash (afaik the damage of God Smash will be doubled on monsters with the Conviction debuff). That’s the main reason.
You will get better damage numbers if you invest silver in +damage % attributes on Smite, Heal and Cure. I’m currently getting 1st or 2nd on Boss damage ranking even against Rank 7 damage classes/DPS builds [only loosing to credit card swiping Archers/Swordsmen] because of Heal&Cure dealing such high amounts of damage [Heal currently at 80% damage/Cure at 70%, both skills lvl 15]. That’s as a physical DEX/CON Cleric with basically only INT classes in his build [Cleric C3>Sadhu C3>Kabbalist C1], so don’t be discouraged so soon.
Get that Five Hammer and get back at them with the power of attributes 
