Price increases:
1. Food: per 12 units bought.
2. Lockpicks: per 36 lockpicks bought.
3. Crystals: per 4 crystals bought.
4. Torches: per 12 bought.
5. Shurikens: per 12 bought.

Factor Increment: 20% (?) for Casual and Hardcore modes. And it is 10% for Real mode. There are also caps per difficulty level/per item.

Anyway, just defeated the first prince. Afterwords, I noticed that the cap on skill training increased, and after 1500 gp, the cost increase is 150 at a time.

Found a Lockpick skill book, but can't use it, and my Gaulen has no skill points to spare at the moment.

Training costs have geometric growth with a bit unusual rounding, there are a total of 100 training sessions, but later sessions require huge sums of gold, so it is unlikely you will be able to afford all 100 sessions.

I paused playing Lords of Xulima for a bit. There was release of Agarest 2 on GOG recently, interesting game to mess around with. Just look at those characters on screenshot! It looks to be quite different from first 2 Agarests though, if first 2 Agarests were more tactical RPGs, Agarest 2 is more like Final Fantasy with open world mode.

I reached the second town and bought a new claymore for my Arcane Soldier. Guess her Flame Strike is going to get even stronger! (And the skill is only level 1.)

Envenomed Strike seems to be a decent skill. At level 1, it does 4 extra damage immediately and 4 poison, which is quite nice (although some enemies take only 3). Still not as good as Flame Strike, however.

After defeating the first prince, I got a lot of money, which I used for training and buying the new weapon.

Incidentally, my Paladin had a Vampiric war hammer. The extra damage from Power Strike doesn't seem to affect the healing from the Vampiric effect, however.

"Vampiric" is still one of the more interesting affixes. Everything which directly increases efficiency is a good thing :)

The problem, of course, is that anything you don't have equipped will weigh down your party. (Oddly, once you equip something, its weight disappears.) My Paladin is now using a flail, but I haven't fought since I got it.

I'm wondering if maybe Gaulen might be better with a one-handed axe so that he can use Venomous Strike more often.

I still haven't checked how weapon changing in battle works.

In the first temple, and while most of the encounters are reasonable (as in, I wouldn't have any serious issues on a higher difficulty), there's a wandering monster in the forest area of Titanic difficulty that has over 2,000 HP. I haven't seen how hard it hits for because the one time I got into battle, the attack missed.

I actually determined that that enemy disappears when you cleanse the temple. interestingly, the other enemies do not. (I reloaded afterwards.)

One odd thing: When my Arcane Soldier attacks the skeletons with her weapon (which does a bit of ice damage normally), I get a message about the cold damage being resisted, but when my mage casts Blizzard, it works. Further, Icy Strike's ice damage still works. (By the way, I have seen as much as 15 burning from Flame Strike level 1, and remember that the attack also does that much damage immediately.)

I found a skill point well that I gave to Gaulen. This is the first targeted skill point gain I have received.

By the way, how is Agarest 2 anyway? You mentioned it being more like Final Fantasy. Is it cutscene heavy like the FF games from 6 onward, or is it more gameplay focused, or is it more like something like Chrono trigger?

Don't forget that some enemies also have negative resistances (and very convoluted calculations behind them).
Each time you make new game, it will randomize bouses from wells and cauldrons. On ym normal playthrough I had my first in rat cave.
It plays in phases. Phase 1: You watch cutscene, which explains story and what you are expected to do. Phase 2: you are free to do whatever you want, until you will reach next "Event" point (with cutscenes). Cutscenes don't stand in the way, and there is button to autoscroll them. Story is actually quite good and well written (I found it more interesting and serious than in Final Fantasy VI-IX). Just to make it clear - this is not waifu simulator as some people say, it actually has quite serious storyline in it (fanservice is very tertiary there...).

First 2 games (Agarest 1 and 0) - you move form dot to dot like in Final Fantasy Tactics, and fights are also tactical (though they don't take that much long time per fight). Agarest 2 discards "tactics" approach, it has free roam world map (but still looks to be dot-based in dungeons) and "simply" turn-based fights. Actual game mechanics are quite deep - there are extended combos, ultimate moves of 2 different kinds, 2 kinds of Break meters. Skill customization looks like science (probably it is easy, but tutorial made it look super convoluted). You also can craft many items, upgrade them, convert into other stuff and so on.

I definitely recommend giving it a go.

A few other notes:

Flame Strike: I think the fire damage/burning is something like (half base damage / 2) plus the bonus from skill level. So if you can do 20 regular damage, you will do around 12.5 or so burning damage. I have actually seen as much as 15 burning damage against thieves. I don't know if enemy armor matters here.

Enemy Thieves: I believe these only flee when at low health. The solution is not to let them act when at low health. If a healthy thief is about to attack, wait until it attacks and then go all-out. Flails and Icy Strike are nice because if you hit the enemy thief, it will be stunned, allowing other attacks to reliably hit. Stone Arrow is also useful because it always hits and does minimum 22 damage when maxed out.
(Hint: Pay attention to the turn order at the right side of the screen.)

A couple more observations:

I did see a Thief (who had not stolen) run when at full health.

Icy Slash does a *lot* of damage. I have seen one attack deal:
24 physical damage
4 damage from the weapon's "icy" property
21 damage from Icy Slash
all for only 6 PP.
(This was done against a Thief, who I would not expect to have an elemental weakness.

That's a lot of damage at this point. (It's not yet possible to do that with a spell.)

Hence why I don't take seriously any other modes except "Normal", as it is hard to keep track of any mechanics. There might be some outgoing spell damage multiplier because of 1st difficulty mode (also did you mean Frost Strike?). Also, was it a critical hit?

I do mean Frost Strike and I am pretty sure it wasn't a critical hit. Also, I have seen as much as 25 Frost Slash damage if lucky (but as little as 15). The weapon used has a base power of 20, so it seems that the extra damage is something like 75-125% of the base damage. (75-125% seems to be how attack and healing spells work.)
Spells do seem to do the listed damage on Normal, in my experience. I did see Level 5 Stone Arrow do 21 damage to a thief once, so it's possible that armor or physical resistance might affect it.

Flame Strike does less extra damage, but it burns for the full amount of the extra damage, which will result in more damage after 2 ticks.

Just cleared the Tower of Resilience. Found a room of fountains, but no skill point ones. Found a room with treasure and skill books of Aura of Protection (which I used) and Flame Strike (which I do not intend to ever use).

During the boss fight, my mage never got to act because of sleep and the damage dealt by Flame Strike (that skill, at level 1, is incredibly powerful with a good weapon). The boss silenced my party, but my bard happened to go next and silence didn't prevent her from using the song that cures silence. (If you don't have a bard, this might be a good spell to have a scroll of handy just in case.)

The enemies in the woods die easily to Flame Strike and drop herbs on death. It seems that all physical attacks have a 100% chance of hitting them. (Is there any way to increase this any higher than that?)

The party is ready to reach level 15. (By the way, my mage did not learn Lightning at the previous level because she already has enough useful spells. Are there any cases where this spell would work well when lower level spells wouldn't?)

Edit: After leveling up, my party has little money and is close to leveling up again. Do you know of any quests around this point that give lots of money but very little experience?