I am very much new to game dev and stuff and really appreciate some help.

basically I am following some online unity tutorials and I am bit confused. Should I go for 3d games or for 2d ones? should I try to make my own game art or copy from somewhere for now?

For art, if you're just getting started it might be easiest to use existing art (unless creating art is something you're interested in). You can find both free and commercial game assets online. (For Unity in particular there's the Unity Asset Store.) Just be sure you have the appropriate rights for whatever assets you use.

2D or 3D is up to you. People sometimes recommend starting with 2D rather than 3D, but with Unity it may not matter as much since a lot of the details are taken care of for you either way.

2D or 3D does not matter in my opinion, i have started with 2D just to learn the flow and grow closer to working on games as before i was doing a lot of system engineering, working with algorithms and seemingly tedious work, game dev gave more of a breathing space and creativity. But the first thing you need to focus is the general idea on what you want to achieve, and work on the first prototype so you have something actually that works and is playable.

For the textures i would use existing or stock images, nothing fancy, just to get a grip of how the game development works, the most important stuff, you will always have time later to update the graphics. By the way, it takes longer to design the game looks that it is to code the logic part.

It is a good thing that you want to start game development before you start working on it, you may need to keep following things in mind:

1.)    Design

2.)   art

3.)   code

4.)   audio

5.)   polish

6.)   marketing.

No matter your skill level, just believe in yourself that you can make a game too. Remember you only get better by doing, failing, then improving.

I would recommend working on your coding skills and polishing that off before focusing on design. as with most programming languages there are multiple ways to do the same thing, some being easier than others, so if you can master your coding you'll be saving yourself alot of time using the shortest route .