Dogecoin is mostly used for tipping posts, but it can be used for general purchases. Dogecoin has had a huge soar in value recently, but I doubt much of the community sees it mainly as an investment coin.
For me it is a spending coin. It is much quicker than the more well known BTC because of more rapid block times, and the current capacity issues of BTC.
Dogecoin, with its very friendly community and relatively high inflation rate, serves as a good entryway into cryptocurrencies, and allows for some experimentation without spending your life savings to figure out how things work.