I had some use of adwords when I launched a friend's channel and then my own. You can reach people instantly, but it could be someone who is curious of the ad but has no interest in your video contents. So the ad must be carefully worded.
There is plenty of ebooks and videos that for free will give you good advice about the ad campaign settings.
Examples are being able to limit the amount of times a single person will see your ad in a day and once they've clicked they don't see it again. This can help you to get a more steady amount of views over a longer period, as it's very easy to burn through your budget in minutes.
Also target to geographic areas, limit the times your ads are shown, and to what demographics.
Then there's the keywords you target, and things like interests etc.
A good setting too is the one where you can input channels to limit your ad to show up on, so for example my ads could just show up on videos by jangbricks for example, who is the biggest LEGO set review related channel.
This means you can ensure only people who should be interested in your content are being targeted.
Even with all of this, I've found the subscribers I gained from advertising are not very motivated to watch or comment, so again, my targeting might not have been perfect.
All stuff to think about. Best of luck!