I try to master as many characters as I can. When I say that I mean every move a character has and not just combos. I like to see how each move with a character as a advantage and disadvantage. So far I've "mastered" really only Sub-Zero, but I am reallly good with Kira,Ashrah, and Mileena. I wouldn't say Jade though, since it doesn't take much skill to pull off her combos that do crazy damage. Still I am still learning how she works as well. When I did play Deception online. I mostly picked a different character each time I played one person. Just to keep things interesting. The characters I had choosen are the characters I mentioned above.That was before I changed my personal policy before people started to wussy out by only do special moves and throws instead of skill with a character. Just before I stopped playing Decpetion online, my policy win or lose people only got one match with me.

I mostly use Havik, Jade, Noob-Smoke, and Kenshi, but I've been trying to master Liu Kang, Baraka and Ermac...

I started out trying to use more than one character because I wanted to win chess kombat and you can't use the same character that you are really good at as both Leader (the most important) and the Grunt (the most numerous piece).
Now I am beginning to want to use more because it is more fun that way and I get to see stuff I haven't seen before.

i play with only my favorite characters so i dont play as characters i hate, but i only mastered a few (ashrah, ermac, kabal, kobra, darrius, liu kang, etc.) but some i still am trying to get good with, i have the ability to play online but i rather not as i cannot stand online gameplay.

I only use Raiden, Ermac, Scorpion, Sub-Zero, Lui, and occasionally I have used Kabal for MK:D.

I switch off between a few people.
Scorpion
Raiden
Shujinko
SubZero
Jade
Noob-Smoke

At first, I was gonna try and master quite a few...
BUT, a couple of months in, I generaly stick with my top 3 of Liu Kang, Kenshi and Sub Zero. I do use others, but I like to stick to those three...

I only use Jade, Ermac, Kabal, Sub-Zero, Scorpion, and Li Mei. I'll only be other characters if I have to beat arcade with them.

I started out playing with my faves (Scorpion Kabal). But after i have a good feel for any character I move on to somebody else till have at least a handfull of characters that I feel comfortable playing with online. I haven't mastered everyone on the board, but I can go random and be pretty confident save a few on the select screen.
But I will always pick BRC or NS if the person I am playing with is whoring them to death.

I dont play with Dairou too much, because I hate him.
The others I play some times
My favorites are Ashrah, Hotaru, Jade, Sindel, Mileena, Baraka and Ermac.

i only know how to use 5
Baraka, Nightwolf, Havik, Scorpion & Ermac

Generaly I play all characters in the game. I have mastered Hotaru pretty
well. Too well I suppose. The others I use are Sub-Zero, Scorpion, Havik,
and Shujinko.

i only used female characters. heres the order i used the most.
1. Li Mei
2. Tanya
3. Ashrah
4. Kira
5. Jade
6. Sindel
i never touch the male characters. NEVER!!!

Wow...i'm sensing some great hostilities there.
anyway my mastered characters are:
Sub-Zero
Scorpion
Ermac
I am currently mastering:
Baraka
Noob Smoke
Jade
Tanya
Mileena
Havik
Kenshi
Li Mei
Kobra
I completely suck with and will probably never master:
Dairou
Hotaru
Raiden
The rest of the characters I don't even use

Shang-Heihachi if you want to play good with Hotaru, use Pi Gua and
Naginata for a start. hotaru can be extremely poverfull and he's good of
keeping anyone at bay / away with his weapon. Timing is crucial. And try
the grasshopper-that rulez for unnerving the human opponents :D

From best to worst:
1. Baraka
2. Liu Kang
3. Scorpion
4. Raiden
5. Ashrah
i ALWAYS play baraka unless i feel like mixing it up a little, or the opponent keeps using a char that requires a certain skill from my other chars.

I love female characters so in every MK game I try to master every female character.So far in MKD I've mastered Mileena,Jade,Tanya,Ashrah,Sindel,and Li Mei.I'm working on Kira.

Here are the chars I masterd and then plan to master
Masterd:
Noob-Smoke
Shujinko
Raiden
Baraka(never use him any more tho cuz he cheap)
Jade
Dairou
Scorpion
Ermac
I Currently Mastering:
Darrius
Kenshi
Havik
Kabal
Lui Kang
The rest idn ill c if i wanna use em or not

I think ive mastered Mileena, but other characters that are super fun are Li Mei, Tanya, Ermac and Liu Kang

I am always, ALWAYS Liu Kang.
Except when I'm not.

I usually master around 6 characters
Mastered so far
Nightwolf
Noob Smoke

well first time playing the game with a quick look at the move list first i had Sub-Zero mastered cuz i mastered him in MKDA. Liu Kang i mastered 2nd when i unlocked him. hes my fav and i missed him in MKDA so for like a couple weeks i only played as Liu and mastered him fairly easily. Noob-Smoke ive also mastered. they're the easiest to master cuz all u gotta do is remember the special moves and like 1 or 2 combos for each. Kira from the start ive had 2/3 mastered. in MKDA some time shortly b4 MKD came out i ended up mastering Kano in MKDA. i hate Sonya tho so i never mastered her so i got a little bit of work with Kira but not much.
Raiden... i was working on mastering him in MKDA but never did so im trying in MKD but he has like the hardest combos and im not too sure ill be able to. and Baraka well.... ive mastered useing the Baraka Blades cuz i seem to always use them when i play as my 3rd fav MKD char. i would rock with Hung Gar if they kept it the same. i hate that they chnaged it. so i got work to do with his unarmed styles hopefully wich wont take too long.
ok other chars im planing to master:
Jade (got her weapon down but thats it)
Tanya (havent really been playing with her and actually may not master her. she interest me tho and im gonna give her a go. probably last tho)
Dairou (form the start have had his first style down. thats pretty much it)
Darrius (got his Guantlets down and actually im pretty close to mastering him. although i dont play with him as much as others so i tend to forget his combos for his first style)
Ashrah (she has an awsome style branch combo. i seem to do it over and over tho. i need to work with her some....)
Ermac (oooo im so close to having him mastered. like Darrius, im having trouble remember his unarmed combos always and actually some times on how to do his specials.)
Scorpion (he was like so easy to master in MKDA. im having such a hard time with him actually in MKD. his first style imo just isnt as good as it was in MKDA.)
i think thats it......
the rest im not gonna master and may never play with again.... Nightwolf for some reason i just cant stand. hes good but i just cant stand him. he just seems so cheap. Kabal is good too but i dont like him still cuz... well im not sure. not having the same Hook Sword combos from MKDA is partially the reason. never liked his character any ways....
Mileena and Hotaru im not mastering cuz i think they truely suck. every one in this game besides these 2 imo r good. Mileena and Hotaru r just the worse and i actually like Cyrax in MKDA better.