Hey guys I'm trying to get into Street Fighter 4 and so far it's been going pretty good. Been playing arcade mode and beating it and when I go online I usually lose 4/5 times but I learn from my mistakes and when I do win I know I did it because I did a specific thing better, like throwing more or timing my ultras perfectly. Anyway currently I play Ken, he's ok I mainly like his speed, and Blanka, wanted to know a charge character so I picked him. I've noticed I don't like slow characters but I don't know who to pick up next. Any suggestions?

Scorpion.

I'm in the same boat. I play Zangief, hit 5k BP and then managed to lose about 500 of it in less than a month. I started trying Dudley, but learning an entirely different character is rough.
 
Try Fei Long.

I play M. Bison, he's a ton of fun. I only win around 40-50% of my matches, so I'm not fantastic or anything, but he's my favorite.

I feel Juri is a fun starting character.

First thing, stop playing in Arcade mode, or atleast don't take it seriously as a measure of how good you are. Secondly, I think it's an important thing to remember in a match, that you don't necessarily have to deplete your enemy's life bar to win. All you have to do is have more life than your opponent when the round is over. It took me a while to realize this, but if you think about it this way it can help you be more patient and focus on punishing your opponent, instead of just going in guns blazing. 
 
About what character you should try. Just play around with characters. Learn their combos, their normals, spend time in training mode, when you're comfortable take it online, go back into training.. etc. It also helps to go to online forums like SRK.com they usually have decent guides listing out BnB combos, links and stuff. Do this with a bunch of different characters and find what you like best. It can take quite a long time, so it may be better not to worry so much about what your "main" is and just have fun experimenting and playing.

Ryu, Ken or Sagat are probably the easiest to learn "and master", but I find Chun-Li or C. Viper to be very good choices as well when you are used to how the game is played. They are both quite fast too, though low on health and damage. If you have the money and the patience I'd recommend learning to play with an arcade stick too, the precision compared to a default 360 controller is fantastic, though it takes a bit of getting used too.

Hakan. He's top tier you know.

Gouken, Ryu, and Akuma are all fairly simple transitions from Ken. Really, though, you should at least know a few moves for a variety of characters (I wouldn't worry too much about, like, Chun-Li or M. Bison, though, as you'd probably never use them). 
 
Ryu and Akuma are also good to learn because Ryu is already confirmed for MvC3, and while I don't think Akuma's been announced, I also don't think Capcom would dare leave him out. He'll probably be unlockable, if they don't straight-up announce him. I'm not sure if Ken will be included, though.

" @RE_Player92:  Guile ... he is very powerful and lends himself to the counterattacking style of gameplay , let the enemy come to you ...hehehe poor bastards "

The way you play you should really play adon and start blocking low.

I main Vega. Despite my temptation to tell you to play him, you probably shouldn't play Vega if you are still getting your grip on the game. Akuma is probably my secondary and a pretty natural transition from Ken, still being a Shoto but having a lot more offensive tools at his disposal. Of course, Akuma is also made of glass and is only second to Seth in terms of dying fast if you screw up. I also really like Bison, so you could try him out.

" You should just jump back into training mode and spend a few minutes with every character. It's that easy. "

Like fast characters?  Try Chun or Akuma.

I play Dhalsim. He's kinda hard to play well, but it's hilarious when people rage because they can't even get close to you.

Cammy?

Believe it or not Ryu is faster than ken.
 
If you really like speed, play akuma, bison, cammy, or any of the other characters with really fast walking speeds.

I was gonna say Gouken but he slow.

" Believe it or not Ryu is faster than ken."

" @TaccyP said:

" Believe it or not Ryu is faster than ken."

Yup, and it's fucking retarded. "

Seth is so much fun to play as a rushdown character, so many options.  Just don't get hit, like, ever.

PICK IBUKI CUZ SHES GOT INSANE CROSSUPS AND POKES AND MEGA MIXUP MINDGAMES YEAAAAAAA

Juri is just plain fun to play as. I really suggest just checking her out at the very least.

Honestly, there are very few characters in ssfiv, if any at all, that are the "wrong choice".  
 
Go do alot of trials, get a find characters that you like how their moves meld together, then play them in training for a bit. 
 Once you get a feel for them take them online and be prepared to learn from your mistakes.

Ibuki is pretty fast.  Abel is quick but I wouldn't say fast.  

I would suggest two things. 
1.Go to trial mode, and try out some trials for ALL the characters, even the ones you don't think you would enjoy (you might surprise yourself) and see if you like the feel of the characters and some of the combos they can do. 
 
2. Also, what I did was that I went for the "get 1000 BP with all characters" trophy/achievement  when I was having trouble picking a main character (I got tired of Cody being ass in a lot of match-ups). That really gave me new insight in all the characters and ultimately made me realize that I still like Cody the best. 
  
oh, if you want a fast character that is sure to annoy people, pick El Fuerte.