You said you tried many times but failed. Well, it depends on how you "try."
If you just go on Reddit and drop links all over the place, you're going to get flagged and banned very quickly.
As you probably already know, Reddit users are not very fond of self-promotion. In fact, they're so sensitive about any kind of promotion that you don't even have to drop a link.
If they can even make a halfway decent argument that you are somehow, someway promoting something, that's usually enough to get your account flagged.
There Is a Better Way
Think of Reddit as a giant forum. To be successful in forum marketing, you have to contribute to the community.
This means taking the time to share information, share truly useful resources you found online, as well as sharing of yourself.
Reddit users view themselves as part of a large community. The key to success involves your willingness to be a genuine member of that community.
Participate. Share what you know. Ask questions.
In other words, be part of an organic community within your target niche.
The Biggest Challenge
The main reason why people struggle with Reddit marketing is because of the fact that it takes quite some time to establish authority and credibility.
Add to this, the natural suspiciousness and skepticism of the typical Reddit user, and you have a big problem on your hands.
It's too easy for marketers to get impatient and just start dropping links all over the place.
Don't do that.
Reddit marketing is a marathon. Focus on sharing value and building a brand around your account.
Pretty soon, once people can trust your account to share only truly useful and valuable information, you can pretty much get away with self-promotion. But you have to be very careful.
You have to mix it in with legit shares and comments. You can't just go on with spam mode and just start blasting links.
Of course, the most common indicator of how well the community views your participation is your Karma score.
The good news with Reddit is once you post a comment or a piece of content that people like, your Karma goes up. Keep at it.
Your job at that point is to find similar content or engage in a similar to keep boosting your karma. That's how you know you're getting on people's good side and building credibility.