Castlevania: Portrait of Ruin

• Skill Points for Jonathan's sub-weapons are gained by hitting an enemy at least once with the sub-weapon and then killing the enemy. If you hit an enemy with multiple sub-weapons only the last to hit gets the xp.

• Don't sell items if you only have 1 of them. Several items that seem like they might be quite common actually appear only once and are needed to complete side quests for much better rewards. For example the Long Sword weapon and Amanita food item.

• If you're willing to do a bit of grinding early on then consider repeatedly killing the first Peeping Eye enemy that appears for headgear that shows where breakable walls are. There are a ton of breakable walls unlike in Dawn of Sorrow and you can find some really nice things behind them.

• Despite all of the story and dialog around the risks of unlocking the full power of the vampire killer, there is no mechanical or narrative downside to unlocking or using it. Its not even discussed after you do it.