If you don't have much experience on home repair, construction, or building then try building a shed in your yard as a beginner's project. You can create your own shed you are not adding onto something else like a fireplace or a deck, rather you are creating something totally new. This makes it easier to design because it won't affect your entire house, so if the design isn't perfect it won't matter too much because the layout of your home won't be affect. If you make any mistakes building your shed then don't worry because the whole look of your home won't be affected. If you don't even finish the shed off then you won't ruin the whole backyard just temporarily made a mess.
You might also want to consider building a shed because it is a really easy first project to do. Most shed designs are very simple and easy to accomplish. If you want to build a tool shed, home workshop, or any other outdoor structure for your home then you don't need to make it pretty or insulated very well. All you need to do is make it sturdy and have it laid out well so you can use it without much trouble. You can also change the design of the shed with no trouble since the designs are so simple. This means that you can create your shed just how you want it for your home and yard. IF you want to try to change a deck from its original design it could be way more difficult and you'll have to work a lot harder to get everything to fit correctly.
Figure out the exact needs of your shred and how you want to use it. For instance if you are building a tool shed then you should know where your tools will go and how you want to store them. You need to figure out what will fit in it and how before you finish the project. When I built my own tool shed I marked the walls in my house to map out how I would store my tools ahead of time. This way I knew how to put the hooks in the right spot from the beginning and I could organize all my supplies ahead of time. This made it so much easier for me when the shed was built because I already knew where everything belonged. One of the best reasons to build a shed is to use it but also just knowing that you created it yourself.