First of all it depends on your competitors. If there are allready hundrets of simular apps in the market you will have a tough to get before them.
And Google takes also downloads and active installs into consideration. So if you manage to get a lot of downloads and people don't delete your app over time you will get ranked higher.
The above isn't complete. Search the web for more information about how the market works.
I read somewhere that new Google Play system holds app for 72h until "second review" with manual operator.
And don't forget that positioning your app depends on many factors, like keywords in the title and description, number of downloads, retention...
Thats why Google Play sucks. I put the same info same title same description on ios and google play. Google play got 50 downloads in 1 month while ios app getse about 20 downloads / Day.
Positioning for the new apps at google play is not good.