Gutters control the water that hits your roof, directing it into a single flow that moves away from your house. Without gutters, it’s possible that water runoff will build up around your home, getting into your foundation and causing water damage over time. Gutters are not able to move water away effectively unless they’re frequently cleaned—and damaged gutters can actually cause more damage than not having gutters at all because they can cause water to pool along your roof.In addition to moving water away, gutters can also help to prevent erosion by controlling water runoff. This protects any landscaping that’s around a property. Without leaf free covers, gutters with  time can get clogged with everything from leaves, pine needles, shingle debris,  etc. This can result in expensive and dangerous home repair costs. Rainwater washing over your gutters can flow around the walls and foundations of your valuable house. This can result in leaky and cracked foundations or flooded basements. 

During a rain storm, the gutters will funnel the water into your downspouts. The water will then flow down the downspouts and out the bottom.  If the water is running over the sides of your gutter or behind your gutter and not out the bottom of the downspout, then you probably have a clog and your gutters are not working properly. Also, you can look for other signs, such as leaks inside your home or basement, plant growth in your gutters, or if your gutters are beginning to pull away from your home.  Damage to your soffit or fascia can also be a sign that the gutters aren't functioning as they should. 

If you are experienced, then yes you can do it. However, climbing ladders and installing the gutters can be dangerous. This is also not a job that can be done with one person.  Most people hire professionals who specialize in gutter installation to take care of the job for them.