
You just need to bear in mind that those echibits in Open could well be Champions or dogs having won out of the earlier classes, so will be much more expereinced.
I would enter say the two first classes plus a Variety class, such as AV (whatever Group your dog is in) or a Stakes class like Any Variety Novice, etc.
With an inexpereinced dog I like to enter 3 classes at Open shows, as often there are not many in a class and the dog is no sooner seen then out of the ring so doesn't really get the4 experince. the mixed classes are great fun and you tend to relax aq bit more as it is apples against oranges so you feel less pressure.