Stacking a tier cake can always be a challenge for the novice baker. Everyone has their preferred way of doing it. I like using fat boba straws or bubble tea straws. Use what you feel comfortable with. This techniques works great with two and three tier cakes. If you are planning to do anything larger four or more layers, this requires even more support so this may not be the technique to use.
Many people like purchasing/making cakes covered with fondant ( sometimes called rolled fondant or plastic icing or sugarpaste or Ready to Roll ( RTL) depending upon the country you are in. And you can even make your own – there are many marshmallow fondant recipes out there.)
You first start out by preparing your cake. The cake gets crumb iced. Remember, the way the cake looks with the crumb ice is close to the way it will appear once coated with fondant. This means dips and bumps, frosting lines may all appear in the finished product. Take you time and do the base right, it will payoff in the end.