The best way to monetize apps (that I have found based on around 6 games and some basic apps):
Ads - There okay if you have a lot of traffic (like angry birds), though there are a few things that can help you if you don’t have millions of people playing your game:
Ad walls - I use Appbrain for this(they have a unity plugin), and then tend to use the revenue generated back into promoting my app, it doesn’t make much but it will still probably be more than admob for low traffic apps Link There are others that do the same so you can check them out if you like.
Banner ads - basically what admob is providing, you will need so many clicks to make anything, I was originally using Mobclix but they decided they didnt actually want to pay me (seriously never use them).
Popups/Interstential - These are great but be careful not to annoy people, I use popups in areas where people aren’t actually playing, like upgrade menus. I also have them come up when you open the app (but not if its the first time They have played the game). I use Heyzap for this, and i also use them for leaderboards and achievement’s. Link to heyzap (they have a unity plugin and they have awesome support).
Freemium - Having your base game for free and then having in-app purchases to either upgrade the game (remove ads, add levels) or add purchasable consumables or extra items. This can be a great way of doing things, but if your adding in stuff that effects game play try and get it balanced so people have an incentive to purchase an item, but know that they don’t have too. I did have a go at this on Amazon with one of my apps but found that just selling a full game and a free game was more effective. for 3 months i used the freemium model and then switched to a paid and free model, with the free and paid i made 36% more revenue(although there could be other things effecting sales during the periods so don’t take this as 100% proof its more effective, it also varies dependant on what kind of app your selling).
Paid App - This is actually what makes me the most money and I find people get caught up in the complexity of trying to get people to but in app items and click on ads when sometimes people just want a full game. Theres also an added bonus of its much easier to get into the top of the top new section in Google with a paid app than a free app.
That should just about do it for that question:)
You can add as many of the same game on Google as you like, normally the free version and the free with in game level purchase would be the same app.
One last note, Google market sucks for trying to get popular, there’s loads of competition, no keyword search and no just in section any more. My best revenue sources are:
Amazon app market - I was sceptical at first, but the thing we should remember is Amazons customers on kindles are used to buying books, so they seem much more open to paying for things.
Apple app store - Similar to amazon, the people using Iphones and Ipads just don’t mind spending money.
Heyzap and Appbrain ads - I covered these above.
Google play - When my app was in the top new section it was actually pretty good, as soon as it left that it dropped to very little, although I get a lot of free app downloads I hardly get any conversions to pay, this is probably the best market for ads/freemium as everyone seems to expect everything to be free ( I actually get negative reviews on the free one complaining some features are only available in the paid version).
If you have any more questions you can add me on Skype at majorsolard(at)hotmail.com or Pm me but it may take a while to respond to Pm’s
Apologies for the bad grammar and formatting, I have a pretty big workload today so I’m rushing a bit.
do I just upload the APK to googleplay and its all good from there ? Sorry to sound like a thicky lol but I seem to have seem a million posts etc to do this but yours is literally drag and drop and go 
Can you put 3 identical games on GooglePlay seperately