1) Be original. Episode reviews and analysis is an over saturated market, which is less likely to get you noticed. People are turned off when someone has exactly the same content as someone else. I can search, for example, "Sleepless in Ponyville analysis" on YouTube and find a ton of them, and they all are about the same. Something I suggest is moving away from the show and more towards the fandom side.
2) nOC. Having an OC is fine, I have one myself, but be careful when using your OC. Never put it in the thumbnail is my advice, but if you do, don't make it the focal point. I can't count how many different thumbnails I've seen that consist of the same three things, an OC, an Equestrian meadow, and a screen shot of the episode. Also, if you use one, stay away from PonyCreator. They look out of place and cheap. My advice would be to stay away from them in general.
3) EDIT EDIT EDIT: If you only listen to one thing, this should be it. Edit your videos. A lot of people will just take the three objects above, record their thoughts, and just leave it be. DONT DO THIS. Even if you aren't doing anything with the video, your voice will need editing. Edit out things like "Well," Umm," and other things you wouldn't want to hear in the video. Its also extremely helpful to have a script ready for recording. You can fond plenty of tutorials on the web for editing.
4) Invest: I watch a lot of gaming on YouTube, and one mistake people make is they will try to get wine on a beer budget, or they try to make good content and do everything right, but their equipment holds them back and hinders video quality. If you are doing commentaries over a screen, make sure to have a good microphone to do it with. Think a Snowball or something like that. If you are going to blog your thoughts, consider investing in a high quality camera or webcam. Paleo is a good example with quality, for example. Basically, if you want your channel to be successful, it will take some investment on your part. You don't have to have golden microphones and movie quality cameras just yet, but keep in mind you at least need a decent start.
5) Copyright: We know YouTube. We know they are quick with the Copyright button. Here's some tips for keeping that nasty copyright virus away.
NEVER use video from the show.
Stills from the show shouldn't take up the video.
I hope I could help you out.
Edit: Also, newer Smart phones have a decent camera for vloging.