Start with smooth plastic, build low quality stuff and reach to a point, a point which you think is considered good enough.
First, take a look at different games and how they have their models and stuff. For the most basic type, you can try looking at this group and it’s games: 13994171
Try copying buildings / models in games, only use one type of material while you do so at the beginning.
Personally, I believe that building with realistic looking materials is a lot more advanced compared to building stuff with simple materials, like smooth plastic.
But, well, it’s your choice after all. Just make sure that you avoid metal and similar materials. ( worst imo )
Yes, you can do that. It’s your choice to be honest.
I suggest you to use the least amount of materials to get used to doing things. After that, you will slowly advance. Don’t expect it to be easy.
You should avoid a number of realistic / bad looking materials while doing so.
Good luck in it. and sorry for the late response.