Hello, I have a few questions.
Hello. I'm an Assassin's Creed player like most of you here. I'm not very skilled at all, since xbox controls are pretty janky 
I was wondering... when the first time you master hidden bladers played AC1, did you have to master the game before you learned at these stunts and exploits? Most of them you cant do now (I believe) since they're all patched up 
But did you have to replay the game multiple times? What video or individual gave you the inspiration to do all of this? Or was it just yourself who decided to do this? How can I improve and maybe find some of my own? (if there are any)
Welcome to The Hidden Blade, magnum. I hope you stick around.
I'm the site admin and co-founder of The Hidden Blade. The site was launched with the AC1 gameplay videos of myself and IanXO4.
Did you have to master the game before you learned at these stunts and exploits?
We certainly mastered the game before designing assassination styles and finding exploits. As someone following a trail already blazed, I would think that you could replicate stunts and exploits with only an intermediate level of skills.
Most of them you cant do now (I believe) since they're all patched up
I cannot think of one cool thing in AC1 that is no longer possible because of a patch. Hell, Ubisoft won't even patch game breaking bugs in AC1 even after we send them video evidence. I've heard that the PC version is slightly different from Xbox/PlayStation, so it may have different exploits.
Did you have to replay the game multiple times?
Yes. I recommend watching this video before your first playthrough (for many, they find it too late). Then master use of the hidden blade by watching this video. For your second playthrough, I recommend a hidden blade only run (no swords or knives). It can be tough in Memory Block 2 when Al Mualim takes away your hidden blade counter ability! Remember the grab-throw-assassinate option.
What video or individual gave you the inspiration to do all of this?
I would thank Firestorm for creating the assassinscreed-maps website (currently offline, don't go to URL and click on malware). He made good maps for flags and Templars. Although Firestorm didn't record gameplay videos himself, he hosted a forum where Assassin's Creed players met and discussed nuances of the game. AC-maps was the blogfather of The Hidden Blade.
Or was it just yourself who decided to do this?
My internal motivation was that I realized late in my first playthrough that I was doing it all wrong. My idea of an assassination was to pull out the long sword, chase the target across town, and swordfight everybody to death. All I knew about the hidden blade was that it didn't work well in a fight. The game did not penalize me for playing poorly so I didn't know any better.
Having cheated myself out of a satisfying playthrough with stealth assassinations of prime targets, I set out to improve my game and make videos so that other players could enjoy AC1 more. I watched every YouTube video I could find but most were just poor gameplay like my first playthrough. IanXO4 was starting around the same time so we collaborated.
How can I improve and maybe find some of my own? (if there are any)
There are still more cool things to be found, especially if you consider the whole AC series. I would first recommend practicing everything: parkour, combat, stealth, air assassinations, etc. The controls are not "janky" once you've mastered them.
Then you must become a student of the game. Watch good gameplay videos, read forums, and make notes of things to try. Sometimes you can take two things that others have found and add them together for a totally new trick. Here are a couple of examples:
YouTuber RikimaruTheHulk did not play Assassin's Creed very long but he created about 25 videos, some with new and interesting discoveries. In Ledge Grab Challenge he showed that Altaïr can survive a fall from any height by grabbing a ledge. In Dropping in the Bureau Rikimaru killed guards on the trap door, dropping their bodies into the Bureau.
IanXO4 took the ledge grab idea, added an air assassination, and invented the crowd favorite Eagle Strike style. With Dropping in the Bureau, IanXO4 thought "What if the person you dropped through the trap door did not die. Maria cannot be killed!". The result was "Imprison Maria": https://www.youtube.com/watch?v=0caTGd2Y358
[Update: Changed "Memory Block 2 when Al Mualim takes away your hidden blade" to clarify "hidden blade counter ability".]
Thanks!
That guide to assassination video really, really helped me. I used to only do 3 investigations and had nowhere to escape!
I've finished AC1 now, and once I finish Syndicate, (currently playing) I'll replay the first one and I'll try to record a "hidden blade only" challenge. Sounds fun! 
Or I'll do a Silent Extermination on a Blighter stronghold, though I have to sharpen up my sneakiness.
Only problem is I have nothing to record a video with. Is there any handy software you use?
I was wondering... when the first time you master hidden bladers played AC1, did you have to master the game before you learned at these stunts and exploits?
Depends what you're trying to do. If it's something like a ghost run or silent extermination, you need practice. When it comes to exploits, it's all about an understanding of and figuring out what can and can't be done with game mechanics. Some of us start exploiting shortly after picking up the game, long before even beating the story.
How it starts when I try to attempt an exploit is saying to myself, "what if I could..." and then proceed to try everything imaginable to achieve that until something eventually works. You can expect to fail many times before you succeed.