Thats not an easy question to answer because variety can play a large part in the yield.
For example I could use alpine strawberries and I would need around twenty to cover the palm of my hand or use Maxim and I would only need two.
Gooseberries can vary in size from about ½" in diameter up to an inch in diameter.
Currants are a bit more consistant but season and protection(or lack of) can affect the yield.
If you mean how much ground a plant takes up I could possibly help you here.
Last week I put this
http://www.allotments4all.co.uk/smf/index.php?topic=32612.0 on the forum and if you wade through that you will get an idea of area required from looking at mine.
There is some information and pictures at;
Currants;
http://tinyurl.com/38k9fh Gooseberries;
http://tinyurl.com/25emzbStrawberries;
http://tinyurl.com/284egsI hope this helps!!
Edit; Having a bit of a problem with some of my linking ??? if you don't get connected to any of the above links, go to the index page on my website and use the alphabetical index
sorry about that!!