Before I go out and spend money on electronics I would like to have some understanding of what various features are available, what they are useful for, and which ones are worth buying. Is there a good website or maybe YouTube presenter to check out?

Fish the moment is a YouTuber who is good at explaining sonars (he uses Humminbird I believe). As far as which brand to get, it’s a Ford vs Chevy vs Dodge deal. Decide what features you want, research the brands and make your decision. The more you educate yourself the better off you’ll be. 

If you can get to a store that has a good selection ask a salesman to show  you what the different units in your price range can do.  Don’t let him go too fast for you to understand what he is doing.  Go back many times until you get the feel of things.  He should be glad to help you because you are the profit.

14 hours ago, 12poundbass said:

Fish the moment is a YouTuber who is good at explaining sonars (he uses Humminbird I believe). As far as which brand to get, it’s a Ford vs Chevy vs Dodge deal. Decide what features you want, research the brands and make your decision. The more you educate yourself the better off you’ll be. 

This is what I was going to say also!  He may use Hummingbird but he has a lot of videos on how the other brands are setup and used also!