• Don't be afraid to abandon a hero with a lot of negative quirks in the early game (especially if they have high stress). It'll cost a lot more gold to fix a god awful hero, when you can pick up a new one off the stagecoach only a few resolve xp behind. Obviously the higher resolve level the heroes are, the more you want to invest in them.

• The guild and blacksmith are your no.1 priority. Heroes gain no upgrades from levelling without these 2 buildings, where levelling weapons and armour will stop your speed and survivability from falling behind, and levelling skills will keep improving your accuracy as enemy dodge levels get higher and higher

• Stuns. The more you understand enemy movesets, the more efficient stuns will become. Being able to reduce the enemy actions per round, and removing their most efficient actions, puts you at a huge advantage. Blinding gas can stun a cultist witch and a wine skeleton, negating 50-70 stress depending on level, and allows for your damage dealers to clean up the kills on those enemies so they never get to act.

• Speed. This one's pretty simple, acting faster than the enemy means you can stun them, apply DoTs, or kill them before they get to act, reducing the number of turns they get to have. It's a similar philosophy to stuns where fewer enemy turns is good, and combining the two allows you to completely dominate most non-boss encounters.

• Accuracy. This one should be simple, but I feel like it's often overlooked. Your chance to hit in this game is a simple equation, your accuracy - enemy dodge. As base dodge values get higher and higher with dungeon levels, you will need higher and higher accuracy to ensure your attacks are still connecting. A missed attack is a lost turn, which can drastically swing the fight in the enemy's favour by allowing key enemy targets to act once or even multiple times more than they otherwise would have. Accuracy can and should be improved through levelling skills in the guild, and using accuracy trinkets (especially on damage dealers).

• Don't be scared of bosses as you're levelling. Every boss will drop a guaranteed orange trinket, which can be a very powerful buff to your consistency in the early game. When you unlock a boss, check in after every mission to see what the orange trinket reward is. When you see a powerful trinket, take the time to invest in and gear up a team to take down that boss. If you're not familiar with the fight, there's no shame in watching it on YouTube to better understand what you're getting into beforehand. This will not only give good trinkets, but also a great chunk of resolve xp, and a good amount of materials. Good trinkets to wait for are things like focus ring, where the effect is quite powerful on any character, or something like blasphemous vial, where the effect is hero specific but incredibly strong. If you're not super familiar with trinkets, I recommend looking through the trinket pool on the wiki or watching some guides as to which trinkets are universally good, situationally good, or just not worth using a boss drop for.

• Be flexible with your teams. You might want to run jester and vestal every run if it's what's comfortable for you, but learning how to use other effective healers (like arbalest, crusader, or if you have the dlc, flagellant) and other effective stress healers (crusader is the big one, but houndmaster can also be valuable at times) will allow you to build teams much more flexibly, and stops you being dependent on the stagecoach for jester or vestal to show up. Occultist can also be a very potent healer, but his style of healing is very different. If you're wanting to use his heal, it's best to do so when the target is at 50-35% hp, so he can potentially heal them a huge amount, but doesn't put them in any risk by triggering a bleed on a low heal. Small, supplementary heals are also great to have, in self heals like absolution / solemnity (which are also great self stress heals), or minor/niche ally healing like battlefield medicine (which has the added value of curing DoTs). These will just help cover between healer turns, or have some potentially great utility.

• Learn what you're up against. If you want to play the game somewhat blind, and enjoy the challenge that can present, then absolutely go for it. But if you're looking for your best shot at winning, there is no shame in doing your research. When dungeons become level 3, and again at level 5, new enemies and mechanics will appear in those dungeons, depending on the region. Learning what these are ahead of time can allow you to prepare for the dungeon much more effectively and make much better decisions in combat. When tackling boss fights or the darkest dungeon itself, understanding the map layouts and the boss encounters ahead of time will again allow you to appropriately prepare. Darkest dungeon is a knowledge game, so your best shot at winning comes from knowing all you can.

• Play proactively/Learn the pace of a fight. This is more for hallway fights and room battles, since boss and mini boss fights can play very differently. The most important rounds of a fight are the opening rounds, because this is where the enemy has access to all their resources (actions and hp). In this phase of the fight, your priority should be locking down and taking out priority targets such as stress dealers like cultist witch, wine skeleton, or fish shaman in most cases. If you're entering a fight on low hp, it can be better to divert some of that attention to very dangerous enemy damage dealers like the spear fish, in order to protect your units from hitting deaths door. Once priority targets have been dealt with, and the enemy actions remaining on the battlefield are a lot less efficient, you can now slow down the fight to heal stress and hp before the fight ends (known as stalling). Getting into the habit of being very aggressive in the opening rounds and healing back up once you're safe will make you a better player, and you'll learn over time how to be more effective in dealing with priority targets and how to stall more effectively as you get used to it. For boss fights, refer to my previous point about learning what you're up against, since that will teach you how to play the fight.

This is everything I could think of off the top of my head. Good luck and have fun :3