‘Goodish’ can mean a large amount (‘add a goodish amount of sugar to the mixture’) and can also mean good but not that good, as in:
That horse has been goodish this season but he has a long way to go before he’s ready for the big race.
The Free Dictionary cites several sources, including this use of goodish from Charles Dickens’ Barnaby Rudge in the person of Solomon Daisy, the parish clerk of Chigwell:
Ay, but then you know,’ returned Solomon Daisy, ‘his house is a goodish way out of London, and they do say that the rioters won’t go more than two miles, or three at the farthest, off the stones.
In The Apple Tree 