When you start a YouTube channel, it will be very difficult to get ranked for those main topic keywords, this is because the main keywords already have competition ranking for them (probably already ranking for many years).
So your best bet is to find low phrases or keywords and try to rank for them, you are looking for keywords and phrases with very low competition.
You can find the low-level keywords by using TubeBuddy, you type in the keyword of your interest in YouTube and then Tubebuddy will tell you the volume and keyword competition, and other similar keywords. I would look for the lowest keywords/phrases and produce videos around those to produce authority in that topic and over time you will start to rank for similar keywords in that subject.
The best strategy is to choose a topic and produce videos around the topic, over time YouTube will take you seriously for that topic because you are promoting authority. But don’t be too broad on the video subjects, you can add other larger topics later.