I am a newbie here and i can totally relate to your topic, it is really hard to make useful post but still i try my very best to put everything i know to a reply so that i can share my thoughts to the community but honestly i don't understand why some people here still do those three things that you have mentioned, plagiarism is such a scary thing to do, most people who do it might just want to earn merit so that they can join campaigns or anything but honestly if you do such thing you will be at risk of being banned or having negative profile so its not a win-win situation, they are just burying themselves.
To be as simple as possible, if you can genuinely contribute to an ongoing discussion without having to prove to anyone that your post are merit worthy by appearing smart with copied works, you'll be just fine on the forum.
This is what i am doing now and i think most of the newbies and even the users who are here for quite sometime do this kinds of replies because putting too much things and points in your reply just to make it look attractive and gain merit but having no sense at all or not being informative because it is just a copied work is just a waste of time, you might not see the karma now but it will hunt you.
Now as a newbie i am practicing some things so that i can be a good user here in the community:
1. Find topic that suits your interest and contribute there, do not force yourself to post replies to a topic that you have no idea just to increase your post count.
2. If ever that you really wanted to post a reply there, make your own research about it and just like the Op said there are youtube and google to get the information that you need.
3. Take your time in your post.
4. Enjoy and have fun here in the forum
