What are some of the best spells early on, first few chapters. I have conjurer and a priest of Lathander.

I'm assuming we're talking about characters of max level 10-11.

After a quick survey I'd like to nominate these:

- Clerical
5th: Chaotic Commands and True Sight
4th: Prot f Evil 10' Radius
3rd: Holy Smite
2nd: Chant, Draw Upon Holy Might
1st: CLW

- Mage
5th: Breach
4th: Stoneskin
3rd: Skull Trap or Fireball
2nd: Web, Mirror Image
1st: Magic Missile

right, thanks.

In the beginning of the game, I'd say Fireball is better than Skull Trap. Skull Trap is better for end-game though, since it has no damage cap.

I don't think you need to know what specific spells to use, but prioritize what types of spells you need. This will not only help you immediately, but as you progress in the game.

I'm not quite sure weather you mean your conjurer and your priest are your only party members, or your only spellcasters. I'll assume for now that you have your everyday party of six, if you don't the strategy I'll outline is still sound, it'll just need some tweaking.

A mage's first priority is to deal with enemy mages, because you meet A LOT of them. Load up on the Breach type spells, and have a couple Dispel effects handy. Second is Area of Effect, fireball type spells are great at giving your tanks an edge in the damage race. I generally avoid AoE's with durations, such as Cloudkill because they really only seem good for cheesy tactics. Third is personal protection such as Stoneskin and Mirror Image. I put it 3rd because you can get the protection you need without having to waste high level slots; nothing is as good as Mirror Image for its level. 4th is summon spells, only a handful are truly exciting, even less are essential. 5th is direct damage, there's just not enough good ones. With this strategy, your 11th level Conjurer might look like this:

5th- 3 Breach, 1 Monster Summoning #3
4th- 2 Stoneskin, 2 Ice Storm
3rd- 3 Fireball/Melf's Minute Meteors, 1 Dispel Magic, 1 Haste
2nd- 3 Mirror Image, 2 Melf's Acid Arrow
1st- 5 Magic Missile

Clerics are much more simple. Healing is of course #1 but I can't tell you how much you're going to need, only you can know that. 2nd is protective spells. 3rd is buffing spells, and the others really don't matter too much until you have a surplus of spell slots. An 10th level priest might look like this:

5th- 2 Mass Cure
4th- 2 Cure Serious Wounds, 1 Neutralize Poison
3rd- 2 Cure Medium Wounds, 1 Dispel Magic
2nd- 2 Slow Poison, 2 Chant
1st- 2 Remove Fear, 2 Cure Light Wounds

These are just rough outlines, and you'll be able to better find out what you need by just playing the game. And sorry about the long-winded reply, but I think it'll serve you better than a one-liner.