For an an electric/acoustic - I'm guessing you mean an acoustic guitar with a pick-up so's you can play through an amp? If it was me, I'd put new strings on straight away - fairly light strings, because it's going to be tough playing barre chords otherwise. On my acoustic guitars, I use 9's - I snapped too many top E strings back in the bad old days when I tried to use 8's. Note - I also use the same gauge on electrics, I like to be able to bend the strings a long way, especially when playing blues.
HOWEVER.....most people would agree that the heavier the strings you put on a guitar, the fuller the tone you get....especially on an acoustic! 10's or 11's are probably the norm, I'd guess...
It's a trade-off - the lighter the strings, the easier to fret....the heavier the strings, the fuller the tone.
It would help, though, if you told us exactly what model of Ovation you've got, possibly with a link to a picture....
Good luck, anyway!
"Sometimes the beauty of music can help us all find strength to deal with all the curves life can throw us." (D. Hodge.)