Here's my two cents.
1) You've got a good voice. Clear and understandable. Good audio.
2) You need to put an image of yourself into your "Let's Play" videos. Gaming viewers want to watch you. It helps them connect to you. They like seeing your reactions. As for how to do so, that depends on the video game you're playing. If there's never really anything that important going on in the upper right-hand corner, you can do an insert image there. However, if there is stuff that viewers will want to see in that corner, use a right-hand column.
If you do show an image of yourself, don't wear a headset but a single ear bud and hide it and its wire from view. Whichever side the camera is on (no matter how slightly), put the ear bud into the opposite ear and then run the wire down your back under your shirt. The more you look like someone the viewer is having a conversation with, the better you'll connect with viewers.
3) Make an intro video for your homepage that is 30 second to a minute long. First talk about which game genre you specialize in on your channel ... then who you are (people subscribe to people, not channel) ... then tell your release schedule ... and then do ONE call-to-action and that is for them to subscribe. Don't monetize your intro video. The intro video is an ad for your channel. Don't have another's ad hurt your ad.
4) Looking over your most recent uploads, you don't seem to have a set release schedule. You need one. Gaming channels are about becoming part of a viewer's daily life. You need to put one out daily but you also need to put it out at the same time everyday. This way your subscribers will begin to expect your content then everyday.
5) Tease, title card, content. You need to hook viewers right away. Title cards don't do that.
6) From a marketing standpoint, putting commercials at the start of a video simply indicates laziness and/or stupidity by the producer. You need to hook your viewers. Like title cards, pre-roll commercials don't hook viewers. They do just the opposite. They work against your show. While viewers wait the five seconds for the "Skip Ad" button to appear, they will at least glance at (if not study) the "Related Videos" column and thus you've just given them the opportunity to think, "Oh, here's a more interesting video to watch." Hook viewers, don't give them an opportunity to click away.
So look at your episodes. Is there structure to them? A natural point where you can do a commercial break. If so, acknowledge it just as they do on TV and incorporate it into your show. As you're a gaming channel, the break point could be between when you doing another attack (i.e., another beach landing in Boom Beach) or before you go into the next room, which is a good point if you're doing a horror game. If your show doesn't have a natural break point, you can create one by adding a new regular segment onto your show. If you cannot think of a new segment, there's always the standby of reading a few of the viewer comments of the previous video.
And as you break away for your commercial break, remind your viewers that you only get paid if they watch the commercial. Crass? Yes, but honest. Most viewers don't know that YouTubers only get paid by YouTube by how many commercials their viewers watch. I would recommend acknowledging this reality and enlisting your viewers' help in financially supporting your channel. "Now for a commercial break, folks. As I only get paid if you watch the commercial in its entirety, I would appreciate if you would. See you after the break." Then after the break, "Thanks for the support, folks. Now let us open that next door."
If you're just slapping a mid-roll ad in wherever, don't. An abrupt break in your episode ticks people off and guarantees they'll hit the "Skip Ad" button to get back to the programming.
As for putting commercials at the end of videos, it would be stupid not to do so since the VAST majority of people will click away once the episode is over. Thus end-roll commercials don't hurt your show. Yes, they produce little income but that's better than nothing.
As for the overlay ads (the banner ads on videos), I would always recommend never allowing those. You've taken so much time and effort to produce a good-looking video and you're now willing to destroy that by allowing a banner ad to be slapped on top of it? And most people click on the little "X" box in the upper right corner of the banner ad to get rid of it as fast as possible. By them doing so, they're not watching your video but focusing on getting rid of the banner ad. The only way I would recommend allowing banner ads is if you incorporate it into your show. "Oh! Banner ad. I will wait while you click it off. [slight pause] Good. Now as I was saying..."
[Now if you absolutely love the games you're playing and would never consider any other game, skip the next two suggestions and go directly to the most important and last suggestion.]
7) Contact gaming companies with a game in alpha. They will be looking to generate buzz for their upcoming game. Look for one that is in the game genre that you have specialized in. Tell them that. Tell them that you're looking for the next big game and you think theirs might be it. Ask to be let into their beta. Once in their beta, do a TON of how-to videos about everything in their game. Don't do "Let's Play" videos during beta as the game isn't set yet and if the released game is different than what you played in the "Let's Play", it will hold little interest to gamers. Email the gaming company weekly. Keep it professional. Ask them if there is anything they would like you to test, check out, do, etc. and then IMMEDIATELY do and release a video on that. Email them once you've uploaded it to your channel and ask for input on it and if there is anything else they'd like to you do a video on. When they go live, start doing "Let's Play" videos since only then is the game "set".
Good gaming companies will want to cultivate you. They might even fly you in to meet the development team. That isn't unheard of. You make a really good video and they might feature it on their website or even give a link to it within the game. When they finally move out of beta and release the "finished" game, you'll be nicely positioned to ride their wave.
As for which gaming companies to contact, I would strongly suggest you look into local gaming companies. You're there. You're a neighbor. You can easily meet with them face to face.
8) Don't tie yourself to any specific game or even franchise but instead do games within a single genre THEN jump onto the next big game. Always keep an eye out for upcoming games, especially mobile games. Very very very few games ever are a surprise to the gaming community. Get into their betas and start producing episodes. When they go live, you're then established. Then when the gaming company generates public interest for their live release, you can then ride their wave. However, never limit yourself to one game. Always keep an eye out for the next big game about to come out, enter its beta, and then ... lather, rinse, repeat.
9) Lastly but most importantly, collaborate, collaborate, and collaborate. You're a very small channel right now but everyone has to start from somewhere. Your best bet is to contact local YouTube channels. As you grow, contact larger and larger gaming channels that match your new size. Always propose an activity for the collaboration and never just that you want to do one. After you release a collaboration video, send links to it to other local YouTubers to show them how you do collaborations and invite them again to do one with you. Go to ALL YouTube conventions that you can afford to go to. Find out who's going and suggest you meet up for at least an interview of them. Doing it while you're at a friendly restaurant gives it a good backdrop. Don't worry about the sound.