Most Helpful Guy
Just keep trying. I know that sounds silly because that's what you've been doing, but trying to gain subscribers is not the easiest. You have to show to people that your content is worth watching by always uploading and improving. Self review your work honestly on how it could have been better, and use that to your advantage to one up the higher rated YT channels. It takes time. All great things do. However, if you put in the time and effort, I'm sure you'll get there.
Most Helpful Girl
Honestly, you need to upload regularly. At least I've a week if you can. And it usually takes a good bit of time before you start getting a significant increase in subscribers, but regularity is the key.
For many people it takes up to a year before they any big changes. The one YouTuber I'm a big fan of, CrankGameplays, didn't really become "famous famous" until about a year or so ago and he's been doing YouTube for like six years