So in the MM the benefits from becoming a vampire are stupidly good for the downsides since you can fix two off the bat. Sunlight and Running Water. Now I don’t know why this isn’t what vampires wear, but why wouldn’t they steal waterproof clothes + Full body cover? I don’t know if I’m wrong about this, but couldn’t just wearing those clothes stopping those problems?
Rant is over about the strange reason why vampires don’t wear clothes like that.
But the reason before I got sidetracked was my question on how to fix transforming into a vampire. The Monster Manual made it far too powerful. So basing it off point buy I think they should get a +1 to +3 to there strength, Dexterity, and Constitution. And one of the vampire traits. Like transforming into a bat or always being affected by spider climb.
Your thoughts?
I used to think that the benefits out way the costs as well until I came across some interesting information. The way I rule it is: You can no longer gain experience points as an undead due to being locked in a stagnant point between life and death.
The rest is just further explanation so, if that's all you needed than that is fine. But if you're curious about my decision on this rule, keep reading. 
Of course, I will be assuming we are talking about the generic undead from the Forgotten Realms settings.
As evidence for this claim -- under "Languages" the MM it states that vampires know "the languages it knew in life"(MM 297). This suggests that proficiencies cannot be attained in undeath, nor can you grow or change(accept through powerful magic such as a "Tome of Understanding" or other similar magic's.).
Vampires, ghosts, ghouls, wights -- in truth, all undead, by their very nature embody a similar theme:
Unfinished. As Romantic Gothic-Horror Archetypes, a vampires unfinished business typically involves betrayal by a loved one, and/or deep sadness turned into irrational rage. They were incomplete in life, and thus stay that way forever, in death. The "Monster Manual" even talks of the dark obsessions that plague vampires -- the "hunger for the life they have lost"(MM 295).
Under "
Dark Desires" it says quote, "[A Vampires]...emotional attachments wither as once-pure feelings become twisted by undeath... In place of emotion, vampires pursue physical symbols of what they crave... [They]...surround themselves with art, books, or sinister items such as torture devices or trophies from creatures they have killed."(MM 295).
So I would ask, why? Why would an immortal creature with nearly limitless resources have a need for books or trophies? It goes without saying that eternity becomes boring without purpose. Without goals to achieve, any time limit to create meaning in existence, or LIFE changes to go through in order to be at peace; one might go mad. Therefore it stands to reason that a vampire would always try to stay busy. From memorizing every book in a library, to learning new languages and skills, to becoming a master artisan; anything that has potential to grow or change so as to keep eternity interesting. In fact, with enough time, there's no reason a vampire wouldn't become a god-like individual with expertise in every proficiency imaginable and possess every Feat in the PHB!
The reason we don't see that is because they lack the natural ability. That collect books and devises because they need reminders of stories, concepts, philosophy, religion, and etc. In D&D, intelligence measures "mental acuity, information recall, and analytical skill"(PHB 12). Intelligence is used to "draw on logic, education, memory, or deductive reasoning"(PHB 177). All of these measurements and abilities are based in priori knowledge. Meaning your inherent ability to reason ANYTHING at all; Which is, of course, automatically applied to everything around you. What I am saying is not that you are stuck with the same proficiencies forever, but you might be able to exchange them for new ones while still retaining your primal potential. For example if you have proficiency in performance, and you want to stop being a proficient performer in order to focus on investigative sciences, over time you could lose the performance bonus and gain an investigation bonus. Doing so doesn't change your economic utility, so I think it's fair. Another reason vampires focus on "...physical symbols of what they crave..."(MM 295) is because they are broken emotionally, and stranded in a world bereft of the basic stimulus needed to feel alive. Their only hope is to surround themselves with unrelenting hobbies derived from one or more incessant obsessions.
Make no mistake, vampirism is
definitely a curse. They remain in constant turmoil throughout their infinitely unchanging fate. And never underestimate the sociological effects of a player character becoming a vampire. How their very existence might be an insult to one or more or the adventuring party's god(s) or patreon(s). Or how any townsfolk will most likely try to kill the character or worse. It's worth mentioning that you first become a vampire spawn, and only become a true vampire if a true vampire relinquishes their blood for you to drink. Otherwise, if the spawns master dies...the spawn simply becomes free willed with a 16 in strength, dexterity, and constitution. That means a lesser form of regeneration, a 60ft darkvision, no shapechange, no charm, no children of the night, no misty escape, and no legendary resistance. You stay chained to the grave at essentially C.R. 5 (b/c you retain level abilities you had prior to being turned) until you are cured of your vampirism or until you become a true vampire.
