Should I save up for iPhone 5s, or just keep my iPhone 5c?

I want iPhone. Not Samsung or Nokia.

What do you want? An iPhone 5c or anything (other than Samsung or Nokia)?

You save up and then when you have the money to get the 5S (full price), then you will have enough to pretty much get anything on the market. Decide what features are important to you, and buy the phone that has all or most of the features that YOU must have.

Keep your iPhone 5c. They have exactly the same features, only one has an extremely cool coloured backing, and the other is just plain metallic!

At this point it would probably be better to go for an iPhone 6 or wait for a 6s (September)

If you have 5C then wait, chances are good when the next iphone comes out, iphone 5S may be free on contract. Then you can't only get that but trade in your 5C and get credit with it. 5C is not that outdated where you need to upgrade now.