On the "Normal" setting, this game is not terribly difficult outside of a few boss fights. I have been playing the game for nearly 20 hours and am around 80% finished with the game. Therefore I would imagine that I am nearly at the end since a lot of the remaining 20% is probably achievements that I have no intention of ever completing anyway.
There are a few tips that I want to offer up to newbies to this (almost) fantastic metroidvania game that has been the only thing I have played the past week or so.
Upgrade your shards as soon as you can
Your primary attack with most weapons is very limited in range for everything other than handguns and the ammo for that can prove tricky and even expensive to maintain. I recommend only using the handgun for boss fights because otherwise you are going to run out very quickly and find yourself running back to the town to purchase more ammo on a regular basis.
Shards on the other hand normally use MP which regenerates slowly and if you have used some there are breakable candles that will always contain MP regen items if you are lacking in it. Your shards control your secondary attacks and these attacks, when powered up, will do substantially more damage than most of your main attacks can do. However, at their base level of 1 they are very weak. They are also very easy to level up and this seriously increases the damage you can do. I find a lot of them useless, such as any of the "summoning" ones that will bring out a temporary ally to fight on your behalf because the helper doesn't stay around very long and their AI is pretty awful as well. Therefore, I would focus on powering up any seeking attack that finds your enemy no matter where they are on the screen, or something directional such as throwing daggers that will do hundreds of HP worth of damage to any enemy that is directly in front of you.
Since the enemy mobs are basically of two types: Really tough ones that stand right in front of you and annoying bounce around the room types that stay out of reach and take pot-shots at you, these two alone are good enough to take care of most of the stuff you will encounter.
If you fail to upgrade these shards most of the offensive "spells" seem rather weak but once you power them up, it is a real game changer.
Consume all the food you can, but only once
This is a tip that I actually ignored myself until I accidentally stumbled upon it while trying to do a silly side quest for this old lady that is always hungry and your objective is to constantly be making her more and more dishes.
Upon first glance, the benefits to cooking for your own use seems counter-productive since it is much more complicated than just buying / making potions and ether (for HP and MP, respectively) but there are other bonuses that come along with them. I never bothered to use more than one of them because I enjoyed the benefit that one of them was giving to me until someone said on a board somewhere that he initial bonus that you receive (blue marks on the left of the above image) are PERMANENT upgrades to your stats.
Therefore, you should cook and consume as many of these dishes as you possibly can but there really isn't much reason to consume them more than once because their non permanent effects are not nearly as good as simply consuming potions.
Once I figured this out my stats got a huge boost and this made a massive difference in my overall power.
Know where to farm
Drops are RNG in this game just like any other and some of the rarer ones have a drop rate something crazy low like 2% and only from specific enemies. You may have to check the ol' internets to figure out where to get a certain item and this was something that I went through when an upgrade I needed required faerie wings.
I felt a bit stupid when I found out by checking an online guide the faerie wings are a 5% drop from guess who? Faeries! I should have known that but the question was finding an area that had enough of them that it would be worth my while. Basically I found a place that had a door next to an area where 2 faeries were always on the other side of it. Since all scenes other than boss battles reset as soon as you leave the area I could endlessly go back and forth and just kill these 2 faeries over and over until I got a bunch of faerie wings, many more than I needed actually.
This is the only time that this game becomes a bit of a grind-fest and of course it is totally up to you if you want to do it but certain items required for upgrades only drop from certain enemies and this is the only way you can go about getting them. The added benefit of this killing of the same enemy over and over is that you are also getting XP for yourself over and over again so if it is a possibility, it is best to go for the toughest version of a particular type of enemy as possible to maximize the value of your time.
Learn bosses "tells" before trying to engage
This might seem quite obvious to anyone who plays a bunch of games, but simply going full speed ahead and attempting to rush a boss to death is likely going to go the opposite way and it is you that is going to end up getting crushed.
For me, this was most evident with the Doppelganger fight because she has this arc flame that she does every now and then that covers 1/3 of the area you are fighting in. This attack is unblockable and you can't duck under it. It also does massive damage and none of your attacks can get through it. Just like any boss in the game, there are certain subtle cues that she is about to do it and you need to high-tail it out of there to safety and wait it out.
Trying to brute-force your way through some of the bosses will actually work in some instances, but you are going to burn a ton of potions in the process and when you consider that hi-potions are 1,000 gold each, you could end up running out of money trying to keep with this process.
The best thing to do when you encounter a boss is to not even try to do any damage until you understand their attack patterns. Of all the bosses I have faced they all tend to have only 3 or 4 types of attacks and for 3/4 of the bosses, one of these attacks always seems to be a "rush" attack that once you understand the "tell" it is very easy to jump over this.
The guns are your best friends in boss battles
Guns have limited functionality in regular exploration because you have limited ammo and while 99 bullets seems like a lot, you will burn through it very quickly. You do have a default ammo that is called "unlimited" and it is exactly that but it is basically a BB gun at that point and does such an insignificant amount of damage that it isn't even worth the trouble of equipping it.
Most of the bosses can't do much to you if you are far away from them but you can do plenty to them at a distance. In fact, it is quite important that you DO stay as far away as possible in most of the fights and this is easy to accomplish if you have the super range of the pistols in your pocket.
Some will say that the ammo is expensive and those people are not wrong. However, it is significantly less expensive than 1000 gold hi-potions and if you choose to fight bosses up close and personal, you will end up using a lot more of these than you will bullets.
Another thing to keep in mind is that when you enter a battle and are using bullets you might feel like you used too many of them because the bosses are capable of blocking them during certain sequences but fear not. All of the boss rooms are directly next to save rooms (thank god) and when you lose or even if you win but you felt like you used too many items the respawning process doesn't take into account the items, including bullets, that you used before, you will respawn with exactly the same gear you had before you entered the battle in the first place.
I believe these tips can help a player to enjoy this game a great deal more and perusing the forums I see a lot of people that were unaware of them and therefore I hope that by doing these things Bloodstained: Ritual of the Night can be a much more rewarding experience.