Be wary of getting a wi-fi speaker. I had a very expensive Bose one and it all worked fine, until and unless I went online on my laptop or iMac. Then it just kept breaking up and stuttering. As soon as I logged out on the computer the speaker was happy again. I took it back to the Apple shop and got a replacement, thinking it was faulty. The replacement behaved just the same. When I took that one back to Apple, I spoke to a different fellow there, who told me that this is a known issue! That was a couple of years ago, so maybe it's been sorted now, but check first.
I ended up buying a small Bose bluetooth speaker and have never had any trouble with it. It's very simple to set up - you just enable your bluetooth on your phone or tablet, then click on something like 'search for other devices'. As long as the bluetooth on your speaker is turned on (there's a bluetooth button on the top of mean that lights up when it's on), it will find it and then you can link them.
Good luck.