A blockage means you probably will have to climb a ladder to inspect your gutters. Chances are, the water is being blocked where the downspout meets the gutter.
It may be possible to clear the gutters by hand. But if you're strong enough and your ladder is sturdy, take the garden hose, with a power spray nozzle attached, up with you. Run it full-force into the downspout.
Check also to see if your gutters are out of alignment. Has a portion of the gutter dipped lower than it should? Will that dip cause water to accumulate there, not allowing it to flow to the nearest downspout?
Dips often can be corrected by simply pushing up on the lower area and using a fastener that goes with the gutter system to hold it up. Most home centers and hardware stores carry lots of brackets for holding gutter systems.
If you don't have downspouts about every 30-35 feet of gutter, you may be in for a problem. Check out the gutter systems sold and installed by companies specializing in gutters and those sold in hardware stores and home centers.
For the most part, gutter system materials come in two types: aluminum and plastic (polyvinylchloride - PVC).
Which type of material is the best? It depends on your house. A copper gutter is probably the longest-lasting, but the expense is not for everyone. Nor would copper look good on every house. Upscale houses are probably the most fitting place for copper gutters.
Gutters made of PVC may last as long as copper, and they're at the low end of the scale price-wise. They usually come in white, earth-tone/brown and maybe one other color, depending on where you live.
Aluminum gutters are priced somewhere between, but usually much closer to PVC. They're generally available in a couple of basic colors; noncolored aluminum gutters can be painted. The advantage here is that they can be painted to match the trim on your house. The disadvantage is that the paint eventually will wear off.