Tales of Berseria

General

You can do everything and unlock everything at whatever difficulty level you please, and change difficulty on the fly throughout the game.

The glowy orb-like Katz souls and the chests they open only unlock cosmetics for most of the game, though opening enough will also unlock some optional gameplay content in the very late game. Katz souls respawn when you leave the overall area.

The in-game map has friendly green markers which point out interesting things like skits, sidequests and voiced NPC conversations. Some events even open up in past areas you might not think to re-visit as you progress through the game, so completionist types especially might want to occasionally check through the maps of towns and their buildings like inns in particular. Fortunately all visited maps can be viewed from anywhere, and missed skits can also be purchased in the postgame.

The optional "code red hunts" are generally worth doing. The game has a key-item system called potentites, where various plot points (often bosses) and strong enemies will give you one. These have a variety of passive effects, most of which are at least somewhat useful, though some won't be applicable below a given difficulty level. There are a lot of code red hunts, so consequently there are a lot of potentites from code red hunts.

Cooking is a full party heal and super cheap, so there's little downside to having someone auto-cook after every battle. Note that both the food's effect and the cook's skill-based effect (like Velvet's stun resistance) only activate if you meet the food's trigger condition (like falling below 40% HP and so on). In other words, if you're more interested in the cook's effect than the food's, pick a food that's easy to trigger consistently.

Herbs should be used right away to permanently boost your stats. They will also regrow over time, but this will take a very long time under normal circumstances so it's not worth trying to regularly check back on them.

While upgrading your existing gear is not critical for beating the game on normal difficulty, over time you can unlock some nice passive bonuses based on a character's cumulative gear upgrade levels (for example +1 max Souls if a characters' gear upgrades add up to +20). These are useful enough that it can be worthwhile to hold on to older but more beefed up gear, at least for the character you prefer to control in fights.

If you're looking to master a lot of gear for their permanent bonuses, gear pieces with extra skill gain on them are worth holding on to in order to speed up the skill learning process. Note that there are 6 party members total, so if you're feeling particularly thorough, you might want to hold on to at least one copy of armors and accessories for the future party members to equip and master. This is not at all necessary for beating the game on Normal though.

You can check which enemies have item drops you haven't acquired yet in the bestiary, though it doesn't check whether or not it's an item you already have a copy of. Note that enemies only drop gear for characters present in your overall party, so especially early on some enemies' item drops are impossible to get until you come back later with a full group.

Focus is a powerful stat especially for Velvet, as it increases the likelihood of stunning enemies. Stunning an enemy not only immediately gains you an extra Soul for longer combos or more Break Souls, but also causes them to take double damage for the duration.

At a certain point in the game you'll get the ability to fight multiple enemy groups at once in the field in a "Dangerous encounter" which can be an efficient way to farm EXP and Grade, though this also scales up the enemy numbers and levels for the fight which can overwhelm your party if you're not careful.

Checking and aiming for enemies' weaknesses, or at least avoiding their resistances, makes fights go much more smoothly, particularly on higher difficulties. An enemy hit in all their elemental and type weaknesses in a single combo (meaning an unbroken chain of Artes which can be extended past the normal limit with Break Soul) causes them to become vulnerable to every attack from every party member for greatly increased damage for as long as you can maintain the combo, indicated by the word "Chain!" showing up near the damage numbers.

It can be hard to keep up with how many Artes into a combo you are in the thick of the fight which is relevant for a number of mechanics (and should not be confused with the Hits counter in the top right corner), but this can be tracked by the number of a character's blue Soul pips that have a white highlight around them. Each Arte in a combo will remove the highlight of one pip, and once none are highlighted, the next Arte will end the combo unless you extend it, typically with using Break Soul.

While not mentioned anywhere in-game, you can activate different characters' Mystic Artes (the powerful mini-cutscene attacks you unlock a little ways into the game) together in a row by holding down the Mystic Arte activation button and a direction button at the end of a Mystic Arte animation, with right/left activating the Mystic Artes of the current members in battle in a sequence, and up/down doing the same for the reserve members. Everyone's Blast Gauge permitting, this even allows using your entire party's Mystic Artes on an enemy essentially all at once for devastating damage.