Hey Winlu, I wanted to ask, how are you making your tilesets? They look so awesome! I love that they are 100% pixelated. May I ask what drawing technique do you have? Is this really like pixelart, one by one pixel? What app do you use for drawing them? 

I think the best thing to have is References. The better they are the easier it is to make it and of course practise and patience.