Order of the blade

I know this was posted over a year ago so you're probably not looking anymore but I do have a few suggestions:

- 5e class features are always unlocked by levels - the Blood Point system is actually a very interesting subversion of that, but your features still need to determine what levels they are unlocked at. It seems that Growing Blade is intended to be the subclass' "core" feature, so it makes sense for that to be the feature unlocked with the order itself at level 3, which works since you need some time to earn Blood Points anyway. However, Blood Hunters also get new order features at levels 7, 10, 15 and 18. For your subclass to be complete, you need to fill out those levels with new features.

- I don't really see a reason why Growing Blade is a linear progression up the Blood Point scale, since it kind of defeats the purpose of using Blood Points instead of just going by character level. If it were instead a list of features of similar point cost that could be chosen out of order, that would feel much more unique, fulfilling and customisable (similar to the way a Warlock's Eldritch Invocations work, for example).

- Growing Blade's first feature serves little to no purpose, as Blood Hunters can freely choose between STR or DEX as their primary attribute, so naturally a Blood Hunter who has a higher DEX is going to use finesse weapons anyway; they don't need this bonus. It would make more sense if other parts of the subclass required a high DEX (perhaps an idea to use for the higher level features?), but as it is now I don't see a reason to need this since if you wanted high damage, you'd be playing high STR already.

- Growing Blade 2 and Blood Knowledge make each other redundant - if you're dealing extra damage to bloodied creatures you probably already know that they're bloodied, no need for an extra class feature to determine that. Also, 'bloodied' isn't technically an official condition in 5e anymore, but that's just semantics since most players know what it means.

- Growing Blade 4 is really awkward since it's a feature you can't use when you need - which is fine, but would be pretty inconvenient most of the time (there's no way of knowing if you'll actually need or even want that bonus damage on your first few attacks). Makes for an interesting decision to make though I suppose. It does seem like you've tried to circumvent that inconvenience with Growing Blade 5, but the micromanagement that gets involved with tracking turns between attacks and the attacks themselves is a little bit much? It could do with being much more simplistic: I'd recommend removing the 3 turn cooldown completely, since you're spending HP to use it anyway so no player is going to want to use it constantly in case they kill themselves with it. Also, you forgot to label how many Blood Points it costs to unlock Growing Blade 5.

- Also on the note of Growing Blade 4, doesn't it kind of overlap with the Blood Hunter's Crimson Rite feature anyway? They pretty much do the same thing, just with slightly different numbers and a different damage type. I'd personally recommend scrapping it entirely and replacing it with something more cohesive with the Order of the Blade's theme of relishing in victory - perhaps a healing effect after killing creatures instead?

- This is far less important, but your flavour text needs a bit of work. The opening paragraph is kind of generic, and could describe literally any hero with an enchanted sword. It doesn't really scream "this theme is unique" to me as I read it. 

All in all you've got a pretty interesting idea that personally I'd love to see finished, but in this current state it's incomplete and pretty messy. Go back to the Blood Hunter rules, read what the original subclasses do, learn, and feel like, and try to imitate that feeling while carving out your own flavour, instead of reinventing the wheel that's unrecognisable against the way all other 5e subclasses function. If you ever come back to this, I'd be excited to see any improvement you make.

Thank you just tell me how I can improve

Very interesting design.